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                                                                   Exhibit 99(c)
 
                 THE TRANSFER OF THIS AGREEMENT IS SUBJECT TO
                  CERTAIN PROVISIONS CONTAINED HEREIN AND TO
                         RESALE RESTRICTIONS UNDER THE
                      SECURITIES ACT OF 1933, AS AMENDED


          STOCK OPTION AGREEMENT, dated January 21, 1997, between Dauphin
Deposit Corporation, a Pennsylvania corporation ("Issuer"), and Allied Irish
Banks, p.l.c., an Irish corporation ("Grantee").

                             W I T N E S S E T H:
                             ------------------- 

          WHEREAS, Grantee and Issuer have entered into an Agreement and Plan of
Merger of even date herewith (the "Merger Agreement"), which agreement has been
executed by the parties hereto immediately prior to this Stock Option Agreement
(the "Agreement"); and

          WHEREAS, as a condition to Grantee's entering into the Merger
Agreement and in consideration therefor, Issuer has agreed to grant Grantee the
Option (as hereinafter defined);

          NOW, THEREFORE, in consideration of the foregoing and the mutual
covenants and agreements set forth herein and in the Merger Agreement, the
parties hereto agree as follows:

          1.  (a)  Issuer hereby grants to Grantee an unconditional, irrevocable
option (the "Option") to purchase, subject to the terms hereof, up to 6,112,088
fully paid and nonassessable shares of Issuer's Common Stock, par value $5.00
per share (together with any associated preferred share purchase rights, "Common
Stock"), at a price of $33 3/16 per share (the "Option Price"); provided,
                                                                -------- 
however, that in no event shall the number of shares of Common Stock for which
-------                                                                       
this Option is exercisable exceed 19.9% of the Issuer's issued and outstanding
shares of Common Stock without giving effect to any shares subject to or issued
pursuant to the Option.  The number of shares of Common Stock that may be
received upon the exercise of the Option and the Option Price are subject to
adjustment as herein set forth.

          (b)  In the event that any additional shares of Common Stock are
either (i) issued or otherwise become outstanding after the date of this
Agreement (other than pursu-
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ant to this Agreement) or (ii) redeemed, repurchased, retired or otherwise cease
to be outstanding after the date of the  Agreement, the number of shares of
Common Stock subject to the Option shall be increased or decreased, as
appropriate, so that, after such issuance, such number equals 19.9% of the
number of shares of Common Stock then issued and outstanding without giving
effect to any shares subject or issued pursuant to the Option.  Nothing
contained in this Section 1(b) or elsewhere in this Agreement shall be deemed to
authorize Issuer or Grantee to breach any provision of the Merger Agreement.

          2.  (a)  The Holder (as hereinafter defined) may exercise the Option,
in whole or part, and from time to time, if, but only if, both an Initial
Triggering Event (as hereinafter defined) and a Subsequent Triggering Event (as
hereinafter defined) shall have occurred prior to the occurrence of an Exercise
Termination Event (as hereinafter defined), provided that the Holder shall have
                                            --------                           
sent the written notice of such exercise (as provided in subsection (e) of this
Section 2) within 90 days following such Subsequent Triggering Event.  Each of
the following shall be an "Exercise Termination Event":  (i) the Effective Time
(as defined in the Merger Agreement) of the Merger; (ii) termination of the
Merger Agreement in accordance with the provisions thereof if such termination
occurs prior to the occurrence of an Initial Triggering Event except a
termination by Grantee pursuant to Section 6.1(c) of the Merger Agreement
(unless the breach by Issuer giving rise to such right of termination is non-
volitional); or (iii) the passage of 12 months after termination of the Merger
Agreement if such termination follows the occurrence of an Initial Triggering
Event or is a termination by Grantee pursuant to Section 6.1(c) of the Merger
Agreement (unless the breach by Issuer giving rise to such right of termination
is non-volitional) (provided that if an Initial Triggering Event continues or
                    --------                                                 
occurs beyond such termination and prior to the passage of such 12-month period,
the Exercise Termination Event shall be 12 months from the expiration of the
Last Triggering Event but in no event more than 18 months after such
termination).  The "Last Triggering Event" shall mean the last Initial
Triggering Event to expire.  The term "Holder" shall mean the holder or holders
of the Option.

          (b)  The term "Initial Triggering Event" shall mean any of the
following events or transactions occurring 

                                      -2-
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after the date hereof:

          (i)   Issuer or any of its Subsidiaries (each an "Issuer Subsidiary"),
     without having received Grantee's prior written consent, shall have entered
     into an agreement to engage in an Acquisition Transaction (as  hereinafter
     defined) with any person (the term "person" for purposes of this Agreement
     having the meaning assigned thereto in Sections 3(a)(9) and 13(d)(3) of the
     Securities Exchange Act of 1934, as amended (the "1934 Act"), and the rules
     and regulations thereunder) other than Grantee or any of its Subsidiaries
     (each a "Grantee Subsidiary") or the Board of Directors of Issuer shall
     have recommended that the stockholders of Issuer approve or accept any
     Acquisition Transaction.  For purposes of this Agreement, "Acquisition
     Transaction" shall mean (w) a merger or consolidation, or any similar
     transaction, involving Issuer or any Significant Subsidiary (as defined in
     Rule 1-02 of Regulation S-X promulgated by the Securities and Exchange
     Commission (the "SEC")) of Issuer, (x) a purchase, lease or other
     acquisition or assumption of all or a substantial portion of the assets or
     deposits of Issuer or any Significant Subsidiary of Issuer, (y) a purchase
     or other acquisition (including by way of merger, consolidation, share
     exchange or otherwise) of securities representing 10% or more of the voting
     power of Issuer, or (z) any substantially similar transaction; provided,
                                                                    -------- 
     however, that in no event shall any merger, consolidation, purchase or
     -------                                                               
     similar transaction involving only the Issuer and one or more of its
     Subsidiaries or involving only any two or more of such Subsidiaries, be
     deemed to be an Acquisition Transaction, provided that any such transaction
     is not entered into in violation of the terms of the Merger Agreement;

          (ii)  Issuer or any Issuer Subsidiary, without having received
     Grantee's prior written consent, shall have authorized, recommended,
     proposed or publicly announced its intention to authorize, recommend or
     propose, to engage in an Acquisition Transaction with any person other than
     Grantee or a 

                                      -3-
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     Grantee Subsidiary, or the Board of Directors of Issuer shall have publicly
     withdrawn or modified, or publicly announced its interest to withdraw or
     modify, in any manner adverse to Grantee, its recommendation that the
     stockholders of Issuer approve the transactions contemplated by the Merger
     Agreement in anticipation of engaging in an Acquisition Transaction;

               (iii)  Any person other than Grantee, any Grantee Subsidiary or
     any Issuer Subsidiary acting in a fiduciary capacity in the ordinary course
     of its business shall have acquired beneficial ownership or the right to
     acquire beneficial ownership of 10% or more of the outstanding shares of
     Common Stock (the term "beneficial ownership" for purposes of this
     Agreement having  the meaning assigned thereto in Section 13(d) of the 1934
     Act, and the rules and regulations thereunder);

               (iv)   Any person other than Grantee or any Grantee Subsidiary
     shall have made a bona fide proposal to Issuer or its stockholders by
     public announcement or written communication that is or becomes the subject
     of public disclosure to engage in an Acquisition Transaction;

               (v)    After an overture is made by a third party to Issuer or
     its stockholders to engage in an Acquisition Transaction, Issuer shall have
     breached any covenant or obligation contained in the Merger Agreement and
     such breach (x) would entitle Grantee to terminate the Merger Agreement and
     (y) shall not have been cured prior to the Notice Date (as defined below);
     or

               (vi)   Any person other than Grantee or any Grantee Subsidiary,
     other than in connection with a transaction to which Grantee has given its
     prior written consent, shall have filed an application or notice with the
     Federal Reserve Board, or other federal or state bank regulatory authority,
     which application or notice has been accepted for processing, for approval
     to engage in an Acquisition Transaction.

          (c)  The term "Subsequent Triggering Event" shall mean either of the
following events or transactions occurring after the date hereof:

                                      -4-
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               (i)  The acquisition by any person of beneficial ownership of 20%
     or more of the then outstanding Common Stock; or
 
               (ii) The occurrence of the Initial Triggering Event described in
     paragraph (i) of subsection (b) of this Section 2, except that the
     percentage referred to in clause (y) shall be 20%.

          (d)  Issuer shall notify Grantee promptly in writing of the occurrence
of any Initial Triggering Event or Subsequent Triggering Event of which it has
notice (together, a "Triggering Event"), it being understood that the giving of
such notice by Issuer shall not be a condition to the right of the Holder to
exercise the Option.

          (e)  In the event the Holder is entitled to and wishes to exercise the
Option, it shall send to Issuer a written notice (the date of which being herein
referred to as  the "Notice Date") specifying (i) the total number of shares it
will purchase pursuant to such exercise and (ii) a place and date not earlier
than three business days nor later than 60 business days from the Notice Date
for the closing of such purchase (the "Closing Date"); provided that if prior
                                                       --------              
notification to or approval of the Federal Reserve Board or any other regulatory
agency is required in connection with such purchase, the Holder shall promptly
file the required notice or application for approval and shall expeditiously
process the same and the period of time that otherwise would run pursuant to
this sentence shall run instead from the date on which any required notification
periods have expired or been terminated or such approvals have been obtained and
any requisite waiting period or periods shall have passed.  Any exercise of the
Option shall be deemed to occur on the Notice Date relating thereto.

          (f)  At the closing referred to in subsection (e) of this Section 2,
the Holder shall pay to Issuer the aggregate purchase price for the shares of
Common Stock purchased pursuant to the exercise of the Option in immediately
available funds by wire transfer to a bank account designated by Issuer,
provided that failure or refusal of Issuer to desig-
--------                                                                   

                                      -5-
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nate such a bank account shall not preclude the Holder from exercising the
Option.

          (g)  At such closing, simultaneously with the delivery of immediately
available funds as provided in subsection (f) of this Section 2, Issuer shall
deliver to the Holder a certificate or certificates representing the number of
shares of Common Stock purchased by the Holder and, if the Option should be
exercised in part only, a new Option evidencing the rights of the Holder thereof
to purchase the balance of the shares purchasable hereunder, and the Holder
shall deliver to Issuer a copy of this Agreement and a letter agreeing that the
Holder will not offer to sell or otherwise dispose of such shares in violation
of applicable law or the provisions of this Agreement.

          (h)  Certificates for Common Stock delivered at a closing hereunder
may be endorsed with a restrictive legend that shall read substantially as
follows:

          "The transfer of the shares represented by this certificate is subject
          to certain provisions of an agreement between the registered holder
          hereof and Issuer and to resale restrictions arising under the
          Securities Act of 1933, as amended.  A copy of such agreement is on
          file at the principal office of Issuer and will be provided to the
          holder hereof  without charge upon receipt by Issuer of a written
          request therefor."

It is understood and agreed that:  (i) the reference to the resale restrictions
of the Securities Act of 1933, as amended (the "1933 Act"), in the above legend
shall be removed by delivery of substitute certificate(s) without such reference
if the Holder shall have delivered to Issuer a copy of a letter from the staff
of the SEC, or an opinion of counsel, in form and substance reasonably
satisfactory to Issuer, to the effect that such legend is not required for
purposes of the 1933 Act; (ii) the reference to the provisions to this Agreement
in the above legend shall be removed by delivery of substitute certificate(s)
without such reference if the shares have been sold or transferred in compliance
with the provisions of this Agreement and under circumstances that do not
require the retention of such reference; and (iii) the legend shall be removed
in its entirety if the conditions in the preceding clauses (i) and (ii) are both
satisfied.  In addition, such certificates 

                                      -6-
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shall bear any other legend as may be required by law.

          (i)  Upon the giving by the Holder to Issuer of the written notice of
exercise of the Option provided for under subsection (e) of this Section 2 and
the tender of the applicable purchase price in immediately available funds, the
Holder shall be deemed to be the holder of record of the shares of Common Stock
issuable upon such exercise, notwithstanding that the stock transfer books of
Issuer shall then be closed or that certificates representing such shares of
Common Stock shall not then be actually delivered to the Holder. Issuer shall
pay all expenses, and any and all United States federal, state and local taxes
and other charges that may be payable in connection with the preparation, issue
and delivery of stock certificates under this Section 2 in the name of the
Holder or its assignee, transferee or designee.

          3.   Issuer agrees: (i) that it shall at all times maintain, free from
preemptive rights, sufficient authorized but unissued or treasury shares of
Common Stock so that the Option may be exercised without additional
authorization of Common Stock after giving effect to all other options,
warrants, convertible securities and other rights to purchase Common Stock; (ii)
that it will not, by charter amendment or through reorganization, consolidation,
merger, dissolution or sale of assets, or by any other voluntary act, avoid or
seek to avoid the observance or performance of any of the covenants,
stipulations or conditions to be observed or performed hereunder by Issuer;
(iii) promptly to take all action as may from time to time be required
(including (x) complying with all premerger notification, reporting and waiting
period requirements specified in 15 U.S.C. (S) 18a and regulations promulgated
thereunder and (y) in the event, under the Bank Holding Company Act of 1956, as
amended (the "BHCA"), or the Change in Bank Control Act of 1978, as amended, or
any state banking law, prior approval of or notice to the Federal Reserve Board
or to any state regulatory authority is necessary before the Option may be
exercised, cooperating fully with the Holder in preparing such applications or
notices and providing such information to the Federal Reserve Board or such
state regulatory authority as they may require) in order to permit the Holder

                                      -7-
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to exercise the Option and Issuer duly and effectively to issue shares of Common
Stock pursuant hereto; and (iv) promptly to take all action provided herein to
protect the rights of the Holder against dilution.

          4.  This Agreement (and the Option granted hereby) are exchangeable,
without expense, at the option of the Holder, upon presentation and surrender of
this Agreement at the principal office of Issuer, for other Agreements providing
for Options of different denominations entitling the holder thereof to purchase,
on the same terms and subject to the same conditions as are set forth herein, in
the aggregate the same number of shares of Common Stock purchasable hereunder.
The terms "Agreement" and "Option" as used herein include any Stock Option
Agreements and related Options for which this Agreement (and the Option granted
hereby) may be exchanged. Upon receipt by Issuer of evidence reasonably
satisfactory to it of the loss, theft, destruction or mutilation of this
Agreement, and (in the case of loss, theft or destruction) of reasonably
satisfactory indemnification, and upon surrender and cancellation of this
Agreement, if mutilated, Issuer will execute and deliver a new Agreement of like
tenor and date. Any such new Agreement executed and delivered shall constitute
an additional contractual obligation on the part of Issuer, whether or not the
Agreement so lost, stolen, destroyed or mutilated shall at any time be
enforceable by anyone.

          5.  In addition to the adjustment in the number of shares of Common
Stock that are purchasable upon exercise of the Option pursuant to Section 1 of
this Agreement, the number of shares of Common Stock purchasable upon the
exercise of the Option and the Option Price shall be subject to adjustment from
time to time as provided in this Section 5.  In the event of any change in, or
distributions in respect of, the Common Stock by reason of stock dividends,
split-ups, mergers, recapitalizations, combinations, subdivisions, conversions,
exchanges of shares, distributions on or in respect of the Common Stock that
would be prohibited under the terms of the Merger Agreement, or the like, the
type and number of  shares of Common Stock purchasable upon exercise hereof and
the Option Price shall be appropriately adjusted in such manner as shall fully
preserve the economic benefits provided hereunder and proper provision shall be
made in any agreement governing any such transaction to provide for such proper
adjustment and the full satisfaction of the Issuer's 

                                      -8-
<PAGE>
 
obligations hereunder.

          6.  Upon the occurrence of a Subsequent Triggering Event that occurs
prior to an Exercise Termination Event, Issuer shall, at the request of Grantee
delivered within 90 days of such Subsequent Triggering Event (whether on its own
behalf or on behalf of any subsequent holder of this Option (or part thereof) or
any of the shares of Common Stock issued pursuant hereto), promptly prepare,
file and keep current a shelf registration statement under the 1933 Act covering
this Option and any shares issued and issuable pursuant to this Option and shall
use its reasonable best efforts to cause such registration statement to become
effective and remain current in order to permit the sale or other disposition of
this Option and any shares of Common Stock issued upon total or partial exercise
of this Option ("Option Shares") in accordance with any plan of disposition
requested by Grantee. Issuer will use its reasonable best efforts to cause such
registration statement first to become effective and then to remain effective
for such period not in excess of 180 days from the day such registration
statement first becomes effective or such shorter time as may be reasonably
necessary to effect such sales or other dispositions. Grantee shall have the
right to demand two such registrations. The foregoing notwithstanding, if, at
the time of any request by Grantee for registration of the Option or Option
Shares as provided above, Issuer is in registration with respect to an
underwritten public offering of shares of Common Stock, and if in the good faith
judgment of the managing underwriter or managing underwriters, or, if none, the
sole underwriter or underwriters, of such offering the inclusion of the Holder's
Option or Option Shares would interfere with the successful marketing of the
shares of Common Stock offered by Issuer, the number of Option Shares otherwise
to be covered in the registration statement contemplated hereby may be reduced;
and provided, however, that after any such required reduction the number of
    --------  -------
Option Shares to be included in such offering for the account of the Holder
shall constitute at least 25% of the total number of shares to be sold by the
Holder and Issuer in the aggregate; and provided further, however, that if such
                                        -------- -------
reduction occurs, then the Issuer shall file a registration statement for the
balance as promptly as practical and no 

                                      -9-
<PAGE>
 
reduction shall thereafter occur. Each such Holder shall provide all information
reasonably requested by Issuer for inclusion in any registration statement to be
filed hereunder. If requested by any such Holder in connection with such
registration, Issuer shall become a party to any underwriting agreement relating
to the sale of such shares, but only to the extent of obligating itself in
respect of representations, warranties, indemnities and other agreements
customarily included in secondary offering underwriting agreements for the
Issuer. Upon receiving any request under this Section 6 from any Holder, Issuer
agrees to send a copy thereof to any other person known to Issuer to be entitled
to registration rights under this Section 6, in each case by promptly mailing
the same, postage prepaid, to the address of record of the persons entitled to
receive such copies. Notwithstanding anything to the contrary contained herein,
in no event shall Issuer be obligated to effect more than two registrations
pursuant to this Section 6 by reason of the fact that there shall be more than
one Grantee as a result of any assignment or division of this Agreement.

          7.  (a)  Immediately prior to the occurrence of a Repurchase Event (as
defined below), (i) following a request of the Holder, delivered prior to an
Exercise Termination Event, Issuer (or any successor thereto) shall repurchase
the Option from the Holder at a price (the "Option Repurchase Price") equal to
the amount by which (A) the Market/Offer Price (as defined below) exceeds (B)
the Option Price, multiplied by the number of shares for which this Option may
then be exercised and (ii) at the request of the owner of Option Shares from
time to time (the "Owner"), delivered within 90 days of such occurrence (or such
later period as provided in Section 10), Issuer shall repurchase such number of
the Option Shares from the Owner as the Owner shall designate at a price (the
"Option Share Repurchase Price") equal to the Market/Offer Price multiplied by
the number of Option Shares so designated.  The term "Market/Offer Price" shall
mean the highest of (i) the price per share of Common Stock at which a tender
offer or exchange offer therefor has been made, (ii) the price per share of
Common Stock to be paid by any third party pursuant to an agreement with Issuer,
(iii) the highest closing price for shares of Common Stock within the six-month
period immediately preceding the date the Holder gives notice of the required
repurchase of this Option or the Owner gives notice of the required repurchase
of Option Shares, as the case may be, or (iv) in the event of a sale of all or a
substantial 

                                     -10-
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portion of Issuer's assets, the sum of the price paid in such sale for such
assets and the current market value of the remaining assets of Issuer as
determined by a nationally recognized investment banking firm mutually selected
by the Holder or the Owner, as the case may be, on the one hand, and the Issuer,
on the other, divided by the number of shares of Common Stock of Issuer
outstanding at the time of such sale. In determining the Market/Offer Price, the
value of consideration other than cash shall be determined by a nationally
recognized investment banking firm mutually selected by the Holder or Owner, as
the case may be, on the one hand, and the Issuer, on the other.

          (b)  The Holder and the Owner, as the case may be, may exercise its
right to require Issuer to repurchase the Option and any Option Shares pursuant
to this Section 7 by surrendering for such purpose to Issuer, at its principal
office, a copy of this Agreement or certificates for Option Shares, as
applicable, accompanied by a written notice or notices stating that the Holder
or the Owner, as the case may be, elects to require Issuer to repurchase this
Option and/or the Option Shares in accordance with the provisions of this
Section 7.  Within the latter to occur of (x) five business days after the
surrender of the Option and/or certificates representing Option Shares and the
receipt of such notice or notices relating thereto and (y) the time that is
immediately prior to the occurrence of a Repurchase Event, Issuer shall deliver
or cause to be delivered to the Holder the Option Repurchase Price and/or to the
Owner the Option Share Repurchase Price therefor or the portion thereof that
Issuer is not then prohibited under applicable law and regulation from so
delivering.

          (c)  To the extent that Issuer is prohibited under applicable law or
regulation from repurchasing the Option and/or the Option Shares in full, Issuer
shall immediately so notify the Holder and/or the Owner and thereafter deliver
or cause to be delivered, from time to time, to the Holder and/or the Owner, as
appropriate, the portion of the Option Repurchase Price and the Option Share
Repurchase Price, respectively, that it is no longer prohibited from delivering,
within five business days after the date on which Issuer is no longer so
prohibited; provided, however, that if Issuer 
            --------  -------                                                

                                     -11-
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at any time after delivery of a notice of repurchase pursuant to paragraph (b)
of this Section 7 is prohibited under applicable law or regulation from
delivering to the Holder and/or the Owner, as appropriate, the Option Repurchase
Price and the Option Share Repurchase Price, respectively, in full (and Issuer
hereby undertakes to use its best efforts to obtain all required regulatory and
legal approvals and to file any required notices as promptly as practicable in
order to accomplish such repurchase), the Holder or Owner may revoke its notice
of repurchase of the Option or the Option Shares either in whole or to the
extent of the prohibition, whereupon, in the latter case, Issuer shall promptly
(i) deliver to the Holder and/or the Owner, as appropriate, that portion of the
Option Repurchase Price or the Option Share Repurchase Price that Issuer is not
prohibited from delivering; and (ii) deliver, as appropriate, either (A) to the
Holder, a new Stock Option Agreement evidencing the right of the Holder to
purchase that number of shares of Common Stock obtained by multiplying the
number of shares of Common Stock for which the surrendered Stock Option
Agreement was exercisable at the time of delivery of the notice of repurchase by
a fraction, the numerator of which is the Option Repurchase Price less the
portion thereof theretofore delivered to the Holder and the denominator of which
is the Option Repurchase Price, or (B) to the Owner, a certificate for the
Option Shares it is then so prohibited from repurchasing.

          (d)  For purposes of this Section 7, a Repurchase Event shall be
deemed to have occurred (i) upon the consummation of any merger, consolidation
or similar transaction involving Issuer or any purchase, lease or other
acquisition of all or a substantial portion of the assets of Issuer, other than
any such transaction which would not constitute an Acquisition Transaction
pursuant to the provisos to Section 2(b)(i) hereof or (ii) upon the acquisition
by any person of beneficial ownership of 50% or more of the then outstanding
shares of Common Stock, provided that no such event shall constitute a
Repurchase Event unless a Subsequent Triggering Event shall have occurred prior
to an Exercise Termination Event.  The parties hereto agree that Issuer's
obligations to repurchase the Option or Option Shares under this Section 7 shall
not terminate upon the occurrence of an Exercise Termination Event unless no
Subsequent Triggering Event shall have occurred prior to the occurrence of an
Exercise Termination Event.

                                     -12-
<PAGE>
 
          8.  (a)  In the event that prior to an Exercise Termination Event,
Issuer shall enter into an agreement (i) to consolidate with or merge into any
person, other than Grantee or one of its Subsidiaries, and shall not be the
continuing or surviving corporation of such consolidation or merger, (ii) to
permit any person, other than Grantee or one of its Subsidiaries, to merge into
Issuer and Issuer shall be the continuing or surviving corporation, but, in
connection with such merger, the then outstanding shares of Common Stock shall
be changed into or exchanged for stock or other securities of any other person
or cash or any other property or the then outstanding shares of Common Stock
shall after such merger represent less than 50% of the outstanding voting shares
and voting share equivalents of the merged company, or (iii) to sell or
otherwise transfer all or substantially all of its  assets to any person, other
than Grantee or one of its Subsidiaries, then, and in each such case, the
agreement governing such transaction shall make proper provision so that the
Option shall, upon the consummation of any such transaction and upon the terms
and conditions set forth herein, be converted into, or exchanged for, an option
(the "Substitute Option"), at the election of the Holder, of either (x) the
Acquiring Corporation (as hereinafter defined) or (y) any person that controls
the Acquiring Corporation.

          (b)  The following terms have the meanings indicated:

               (1)  "Acquiring Corporation" shall mean (i) the continuing or
     surviving corporation of a consolidation or merger with Issuer (if other
     than Issuer), (ii) Issuer in a merger in which Issuer is the continuing or
     surviving person, and (iii) the transferee of all or substantially all of
     Issuer's assets.

               (2)  "Substitute Common Stock" shall mean the common stock issued
     by the issuer of the Substitute Option upon exercise of the Substitute
     Option.

               (3)  "Assigned Value" shall mean the Market/Offer Price, as
     defined in Section 7.

                                     -13-
<PAGE>
 
               (4)  "Average Price" shall mean the average closing price of a
     share of the Substitute Common Stock for the one year immediately preceding
     the consolidation, merger or sale in question, but in no event higher than
     the closing price of the shares of Substitute Common Stock on the day
     preceding such consolidation, merger or sale; provided that if Issuer is
                                                   --------                  
     the issuer of the Substitute Option, the Average Price shall be computed
     with respect to a share of common stock issued by the person merging into
     Issuer or by any company which controls or is controlled by such person, as
     the Holder may elect.

          (c)  The Substitute Option shall have the same terms as the Option,
provided, that if the terms of the Substitute Option cannot, for legal reasons,
--------                                                                       
be the same as the Option, such terms shall be as similar as possible and in no
event less advantageous to the Holder.  The issuer of the Substitute Option
shall also enter into an agreement with the then Holder or Holders of the
Substitute Option in substantially the same form as this Agreement, which shall
be applicable to the Substitute Option.

          (d)  The Substitute Option shall be exercisable for such number of
shares of Substitute Common Stock as is equal to the Assigned Value multiplied
by the number of shares of Common Stock for which the Option is then
exercisable, divided by the Average Price.  The exercise price of the Substitute
Option per share of Substitute Common Stock shall then be equal to the Option
Price multiplied by a fraction, the numerator of which shall be the number of
shares of Common Stock for which the Option is then exercisable and the
denominator of which shall be the number of shares of Substitute Common Stock
for which the Substitute Option is exercisable.

          (e)  In no event, pursuant to any of the foregoing paragraphs, shall
the Substitute Option be exercisable for more than 19.9% of the shares of
Substitute Common Stock outstanding prior to exercise of the Substitute Option.
In the event that the Substitute Option would be exercisable for more than 19.9%
of the shares of Substitute Common Stock outstanding prior to exercise but for
this clause (e), the issuer of the Substitute Option (the "Substitute Option
Issuer") shall make a cash payment to Holder equal to the excess of (i) the
value of the Substitute Option without giving effect to the limitation in this
clause (e) over 

                                     -14-
<PAGE>
 
(ii) the value of the Substitute Option after giving effect to the limitation in
this clause (e). This difference in value shall be determined by a nationally
recognized investment banking firm selected by the Holder or the Owner, as the
case may be, and reasonably acceptable to the Acquiring Corporation.

          (f)  Issuer shall not enter into any transaction described in
subsection (a) of this Section 8 unless the Acquiring Corporation and any person
that controls the Acquiring Corporation assume in writing all the obligations of
Issuer hereunder.

          9.  (a)  At the request of the holder of the Substitute Option (the
"Substitute Option Holder"), the Substitute Option Issuer shall repurchase the
Substitute Option from the Substitute Option Holder at a price (the "Substitute
Option Repurchase Price") equal to (x) the amount by which (i) the Highest
Closing Price (as hereinafter defined) exceeds (ii) the exercise price of the
Substitute Option, multiplied by the number of shares of Substitute Common Stock
for which the Substitute Option may then be exercised plus (y) Grantee's
reasonable out-of-pocket expenses (to the extent not previously reimbursed), and
at the request of the owner (the "Substitute Share Owner") of shares of
Substitute Common Stock (the "Substitute Shares"), the Substitute Option Issuer
shall repurchase the Substitute Shares at a price (the "Substitute Share
Repurchase Price") equal to (x) the Highest Closing Price multiplied by the
number of Substitute Shares so designated plus (y) Grantee's reasonable Out-of-
Pocket Expenses (to the extent not previously reimbursed). The term "Highest
Closing Price" shall mean the highest closing price for shares of Substitute
Common Stock within the six-month period immediately preceding the date the
Substitute Option Holder gives notice of the required repurchase of the
Substitute Option or the Substitute Share Owner gives notice of the required
repurchase of the Substitute Shares, as applicable.

          (b)  The Substitute Option Holder and the Substitute Share Owner, as
the case may be, may exercise its respective right to require the Substitute
Option Issuer to 

                                     -15-
<PAGE>
 
repurchase the Substitute Option and the Substitute Shares pursuant to this
Section 9 by surrendering for such purpose to the Substitute Option Issuer, at
its principal office, the agreement for such Substitute Option (or, in the
absence of such an agreement, a copy of this Agreement) and certificates for
Substitute Shares accompanied by a written notice or notices stating that the
Substitute Option Holder or the Substitute Share Owner, as the case may be,
elects to require the Substitute Option Issuer to repurchase the Substitute
Option and/or the Substitute Shares in accordance with the provisions of this
Section 9. As promptly as practicable, and in any event within five business
days after the surrender of the Substitute Option and/or certificates
representing Substitute Shares and the receipt of such notice or notices
relating thereto, the Substitute Option Issuer shall deliver or cause to be
delivered to the Substitute Option Holder the Substitute Option Repurchase Price
and/or to the Substitute Share Owner the Substitute Share Repurchase Price
therefor or, in either case, the portion thereof which the Substitute Option
Issuer is not then prohibited under applicable law and regulation from so
delivering.

          (c)  To the extent that the Substitute Option Issuer is prohibited
under applicable law or regulation from repurchasing the Substitute Option
and/or the Substitute Shares in part or in full, the Substitute Option Issuer
following a request for repurchase pursuant to this Section 9 shall immediately
so notify the Substitute Option Holder and/or the Substitute Share Owner and
thereafter deliver or cause to be delivered, from time to time, to the
Substitute Option Holder and/or the Substitute Share Owner, as appropriate, the
portion of the Substitute Share Repurchase Price, respectively, which it is no
longer prohibited from delivering,  within five business days after the date on
which the Substitute Option Issuer is no longer so prohibited; provided,
                                                               -------- 
however, that if the Substitute Option Issuer is at any time after delivery of a
-------                                                                         
notice of repurchase pursuant to subsection (b) of this Section 9 prohibited
under applicable law or regulation from delivering to the Substitute Option
Holder and/or the Substitute Share Owner, as appropriate, the Substitute Option
Repurchase Price and the Substitute Share Repurchase Price, respectively, in
full (and the Substitute Option Issuer shall use its best efforts to receive all
required regulatory and legal approvals as promptly as practicable in order to
accomplish such repurchase), the Substitute Option 

                                     -16-
<PAGE>
 
Holder or Substitute Share Owner may revoke its notice of repurchase of the
Substitute Option or the Substitute Shares either in whole or to the extent of
the prohibition, whereupon, in the latter case, the Substitute Option Issuer
shall promptly (i) deliver to the Substitute Option Holder or Substitute Share
Owner, as appropriate, that portion of the Substitute Option Repurchase Price or
the Substitute Share Repurchase Price that the Substitute Option Issuer is not
prohibited from delivering; and (ii) deliver, as appropriate, either (A) to the
Substitute Option Holder, a new Substitute Option evidencing the right of the
Substitute Option Holder to purchase that number of shares of the Substitute
Common Stock obtained by multiplying the number of shares of the Substitute
Common Stock for which the surrendered Substitute Option was exercisable at the
time of delivery of the notice of repurchase by a fraction, the numerator of
which is the Substitute Option Repurchase Price less the portion thereof
theretofore delivered to the Substitute Option Holder and the denominator of
which is the Substitute Option Repurchase Price, or (B) to the Substitute Share
Owner, a certificate for the Substitute Common Shares it is then so prohibited
from repurchasing.

          10.  The 90-day period for exercise of certain rights under Sections
2, 6, 7 and 13 shall be extended:  (i) to the extent necessary to obtain all
regulatory approvals for the exercise of such rights, and for the expiration of
all statutory waiting periods; and (ii) to the extent necessary to avoid
liability under Section 16(b) of the 1934 Act by reason of such exercise.

          11.  Issuer hereby represents and warrants to Grantee as follows:

          (a)  Issuer has full corporate power and authority to execute and
deliver this Agreement and to consummate the transactions contemplated hereby.
The execution and delivery of this Agreement and the consummation of the
transactions contemplated hereby have been duly and validly authorized by the
Board of Directors of Issuer and no other corporate proceedings on the part of
Issuer are necessary to authorize this Agreement or to consummate the
transactions so contemplated. This Agreement has been duly and validly

                                     -17-
<PAGE>
 
executed and delivered by Issuer.

          (b)  Issuer has taken all necessary corporate action to authorize and
reserve and to permit it to issue, and at all times from the date hereof through
the termination of this Agreement in accordance with its terms will have
reserved for issuance upon the exercise of the Option, that number of shares of
Common Stock equal to the maximum number of shares of Common Stock at any time
and from time to time issuable hereunder, and all such shares, upon issuance
pursuant hereto, will be duly authorized, validly issued, fully paid,
nonassessable, and will be delivered free and clear of all claims, liens,
encumbrance and security interests and not subject to any preemptive rights.

          (c)  Issuer has taken all action (including if required redeeming all
of the Rights or amending or terminating the Rights Agreement) so that the
entering into of this Option Agreement, the acquisition of shares of Common
Stock hereunder and the other transactions contemplated hereby do not and will
not result in the grant of any rights to any person under the Rights Agreement
or enable or require the Rights to be exercised, distributed or triggered.

          12.  Grantee hereby represents and warrants to Issuer that:

          (a)  Grantee has all requisite corporate power and authority to enter
into this Agreement and, subject to any approvals or consents referred to
herein, to consummate the transactions contemplated hereby.  The execution and
delivery of this Agreement and the consummation of the transactions contemplated
hereby have been duly authorized by all necessary corporate action on the part
of Grantee.  This Agreement has been duly executed and delivered by Grantee.

          (b)  The Option is not being, and any shares of Common Stock or other
securities acquired by Grantee upon exercise of the Option will not be, acquired
with a view to the public distribution thereof and will not be transferred or
otherwise disposed of except in a transaction registered or exempt from
registration under the Securities Act.

          13.  Neither of the parties hereto may assign any of its rights or
obligations under this Option Agreement or the Option created hereunder to any
other person, without 

                                     -18-
<PAGE>
 
the express written consent of the other party, except that in the event a
Subsequent Triggering Event shall have occurred prior to an Exercise Termination
Event, Grantee, subject to the express provisions hereof, may assign in whole or
in part its rights and obligations hereunder within 90 days following such
Subsequent Triggering Event (or such later period as provided in Section 10);
provided, however, that until the date 15 days following the date on which the
--------  -------
Federal Reserve Board approves an application by Grantee under the BHCA to
acquire the shares of Common Stock subject to the Option, Grantee may not assign
its rights under the Option except in (i) a widely dispersed public
distribution, (ii) a private placement in which no one party acquires the right
to purchase in excess of 2% of the voting shares of Issuer, (iii) an assignment
to a single party (e.g., a broker or investment banker) for the purpose of
                   -----
conducting a widely dispersed public distribution on Grantee's behalf, or (iv)
any other manner approved by the Federal Reserve Board.

          14.  Each of Grantee and Issuer will use its best efforts to make all
filings with, and to obtain consents of, all third parties and governmental
authorities necessary to the consummation of the transactions contemplated by
this Agreement, including without limitation making application to list the
shares of Common Stock issuable hereunder on the New York Stock Exchange upon
official notice of issuance and applying to the Federal Reserve Board under the
BHCA for approval to acquire the shares issuable hereunder, but Grantee shall
not be obligated to apply to state banking authorities for approval to acquire
the shares of Common Stock issuable hereunder until such time, if ever, as it
deems appropriate to do so.

          15.  The parties hereto acknowledge that damages would be an
inadequate remedy for a breach of this Agreement by either party hereto and that
the obligations of the parties hereto shall be enforceable by either party
hereto through injunctive or other equitable relief.

          16.  If any term, provision, covenant or restriction contained in this
Agreement is held by a court or a federal or state regulatory agency of
competent jurisdiction to be invalid, void or unenforceable, the remainder of
the

                                     -19-
<PAGE>
 
terms, provisions and covenants and restrictions contained in this Agreement
shall remain in full force and effect, and shall in no way be affected, impaired
or invalidated. If for any reason such court or regulatory agency determines
that the Holder is not permitted to acquire, or Issuer is not permitted to
repurchase pursuant to Section 7, the full number of shares of Common Stock
provided in Section 1(a) hereof (as adjusted pursuant to Section 1(b) or 5
hereof), it is the express intention of Issuer to allow the Holder to acquire or
to require Issuer to repurchase such lesser number of shares as may be
permissible, without any amendment or modification hereof.

          17.  All notices, requests, claims, demands and other communications
hereunder shall be deemed to have been duly given when delivered in person, by
cable, telegram, telecopy or telex, or by registered or certified mail (postage
prepaid, return receipt requested) at the respective addresses of the parties
set forth in the Merger Agreement.

          18.  This Agreement shall be governed by and construed in accordance
with the laws of the State of Pennsylvania, regardless of the laws that might
otherwise govern under applicable principles of conflicts of laws thereof.

          19.  This Agreement may be executed in two or more counterparts, each
of which shall be deemed to be an original, but all of which shall constitute
one and the same agreement.

          20.  Except as otherwise expressly provided herein, each of the
parties hereto shall bear and pay all costs and expenses incurred by it or on
its behalf in connection with the transactions contemplated hereunder, including
fees and expenses of its own financial consultants, investment bankers,
accountants and counsel.

          21.  Except as otherwise expressly provided herein or in the Merger
Agreement, this Agreement contains the entire agreement between the parties with
respect to the transactions contemplated hereunder and supersedes all prior
arrangements or understandings with respect thereof, written or oral.  The terms
and conditions of this Agreement shall inure to the benefit of and be binding
upon the parties hereto and their respective successors and permitted assigns.
Nothing in this Agreement, expressed or implied, 

                                     -20-
<PAGE>
 
is intended to confer upon any party, other than the parties hereto, and their
respective successors except as assigns, any rights, remedies, obligations or
liabilities under or by reason of this Agreement, except as expressly provided
herein.

          22.  Capitalized terms used in this Agreement and not defined herein
shall have the meanings assigned thereto in the Merger Agreement.

                                     -21-
<PAGE>
 
          IN WITNESS WHEREOF, each of the parties has caused this Agreement to
be executed on its behalf by its officers thereunto duly authorized, all as of
the date first above written.


                              DAUPHIN DEPOSIT CORPORATION


 
                              By: /s/ C.R. Jennings
                                 ----------------------------------
                                 Name: Christopher R. Jennings
                                 Title: Chairman of the 
                                   Board and Chief Executive 
                                   Officer



                              ALLIED IRISH BANKS, P.L.C.



                              By: /s/ J.E. Casey
                                 ----------------------------------
                                 Name: Jeremiah E. Casey
                                 Title: Chief Executive, USA      
                                   Division

                                     -22-