Exhibit 10

                                OPTION AGREEMENT

         OPTION AGREEMENT ("Option Agreement") dated May 21, 1997, among Charter
One Financial, Inc. ("COFI"), a Delaware corporation registered as a savings and
loan holding company under the Home Owners' Loan Act, as amended ("HOLA"), and
RCSB Financial, Inc. ("RCSB"), a Delaware corporation registered as a savings
and loan holding company under HOLA.

                              W I T N E S S E T H:

         WHEREAS, the Boards of Directors of COFI and RCSB have approved an
Agreement and Plan of Merger and Reorganization dated as of even date herewith
(the "Merger Agreement") providing for, among other things, the merger of RCSB
with and into a subsidiary of COFI;

         WHEREAS, as a condition to COFI entering into the Merger Agreement,
COFI has required that RCSB agree, and RCSB has agreed, to grant to COFI the
option set forth herein to purchase authorized but unissued shares of COFI
Common Stock.

         NOW, THEREFORE, in consideration of the premises herein contained, the
parties agree as follows:

         1.  Definitions.
             -----------

         Capitalized terms used but not defined herein shall have the same
meanings as in the Merger Agreement.



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         2.       Grant of Option.
                  ---------------

         Subject to the terms and conditions set forth herein, RCSB hereby
grants to COFI an option (the "Option") to purchase from RCSB up to 2,880,944
authorized and unissued shares of RCSB Common Stock at a price of $37.50 per
share (the "Purchase Price") payable in cash as provided in Section 4 hereof.

         3.       Exercise of Option.
                  ------------------

         (a) COFI may exercise the Option, in whole or in part, at any time or
from time to time if a Purchase Event (as defined below) shall have occurred;
PROVIDED, HOWEVER, that (i) to the extent the Option shall not have been
exercised, it shall terminate and be of no further force and effect upon the
earliest to occur of (A) the Effective Time of the Company Merger, (B) the
termination of the Merger Agreement in accordance with Section 7.1 other than a
termination by COFI pursuant to Section 7.1(d) thereof, and (C) eighteen months
following the termination of the Merger Agreement by COFI in accordance with
Section 7.1(d) thereof, PROVIDED that if such termination pursuant to subpart
(B) above follows an Extension Event (as defined below), the Option shall not
terminate until the date that is 12 months following such termination; (ii) if
the Option cannot be exercised on such day because of any injunction, order or
similar restraint issued by a court of competent jurisdiction, the Option shall
expire on the 30th business day after such injunction, order or restraint shall
have been dissolved or when such injunction, order or restraint shall have
become permanent and no longer subject to appeal, as the case may be; and (iii)
that any such exercise shall be subject to compliance with applicable law,
including the HOLA.

         (b)      As used herein, a "Purchase Event" shall mean any of the 
following events:

                  (i)      RCSB or any of the RCSB Subsidiaries, without having
     received prior written consent from COFI, shall have entered into,
     authorized, recommended, proposed or publicly

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         announced its intention to enter into, authorize, recommend, or
         propose, an agreement, arrangement or understanding with any person
         (other than COFI or an COFI Subsidiary to (A) effect a merger or
         consolidation or similar transaction involving RCSB or any RCSB
         Subsidiary (other than internal mergers, reorganizing actions,
         consolidations or dissolutions involving only existing RCSB
         Subsidiaries), (B) purchase, lease or otherwise acquire 35% or more of
         the consolidated assets of RCSB, or (C) purchase or otherwise acquire
         (including by way of merger, consolidation, share exchange or similar
         transaction) Beneficial Ownership (as defined below) of common stock
         representing 20% or more of the voting power of RCSB or any RCSB
         Subsidiary;

                  (ii) any person or group (other than COFI or an COFI
         Subsidiary, or RCSB or any RCSB Subsidiary acting in a fiduciary
         capacity) shall have acquired Beneficial Ownership or the right to
         acquire Beneficial Ownership of 20% or more of the voting power of
         RCSB; or

                  (iii) RCSB's Board of Directors shall have withdrawn or
         modified in a manner adverse to COFI the recommendation of the Board of
         Directors with respect to the Merger Agreement and the Company Merger,
         in each case after an Extension Event; or

                  (iv) the holders of RCSB Common Stock shall not have approved
         the Merger Agreement and the Company Merger at the RCSB stockholders'
         meeting held for such purpose, or such meeting shall not have been held
         or shall have been canceled prior to termination of the Merger
         Agreement in accordance with its terms, in each case after an Extension
         Event. (c) As used herein, the term "Extension Event" shall mean any of
         the following events:

                  (i)  a Purchase Event of the type specified in clauses (b) 
         (i) and (b) (ii) above;

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                  (ii) any person or group (other than COFI or an COFI
         Subsidiary,) shall have "commenced" (as such term is defined in Rule
         14d-2 under the Exchange Act), or shall have filed a registration
         statement under the Securities Act with respect to, a tender offer or
         exchange offer to purchase shares of RCSB Common Stock such that, upon
         consummation of such offer, such person or group would have Beneficial
         Ownership or the right to acquire Beneficial Ownership of 20% or more
         of the voting power of RCSB;

                  (iii) any person or group (other than COFI or an COFI
         Subsidiary) shall have publicly announced its willingness, or shall
         have publicly announced a proposal, or publicly disclosed an intention
         to make a proposal, (x) to make an offer described in clause (ii) above
         or (y) to engage in a transaction described in clause (i) above; or

                  (iv) any person, by public proxy, consent solicitation or
         other process made to the RCSB stockholders, shall seek proxies in
         opposition to the Merger Agreement and Company Merger. (d) As used
         herein, the terms "Beneficial Ownership" and "Beneficially Own" shall
         have the meanings ascribed to them in Rule 13d-3 under the Exchange 
         Act.

         (e) In the event COFI wishes to exercise the Option, it shall deliver
to RCSB a written notice (the date of which being herein referred to as the
"Notice Date") specifying (i) the total number of shares of RCSB Common Stock it
intends to purchase pursuant to such exercise and (ii) a place and date not
earlier than three business days nor later than 60 calendar days from the Notice
Date for the closing of such purchase (the "Closing Date").

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         4.       Payment and Delivery of Certificates.
                  ------------------------------------

         (a) At the closing referred to in Section 3 hereof, COFI shall pay to
RCSB the aggregate Purchase Price for the shares of RCSB Common Stock purchased
pursuant to the exercise of the Option in immediately available funds by wire
transfer to a bank account designated by RCSB.

         (b) At such closing, simultaneously with the delivery of cash as
provided in Section 4(a), RCSB shall deliver to COFI a certificate or
certificates representing the number of shares of RCSB Common Stock purchased by
COFI, registered in the name of COFI or a nominee designated in writing by COFI,
and COFI shall deliver to RCSB a letter agreeing that COFI shall not offer to
sell, pledge or otherwise dispose of such shares in violation of applicable law
or the provisions of this Option Agreement.

         (c) If at the time of issuance of any RCSB Common Stock pursuant to any
exercise of the Option, RCSB shall have issued any share purchase rights or
similar securities to holders of RCSB Common Stock, then each such share of RCSB
Common Stock shall also represent rights with terms substantially the same as
and at least as favorable to COFI as those issued to other holders of RCSB
Common Stock.

         (d) Certificates for RCSB Common Stock delivered at any closing
hereunder shall be endorsed with a restrictive legend which 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 RCSB Financial, Inc. dated May 21, 1997, a copy of which is
         on file at the principal office of RCSB Financial, Inc., and to resale
         restrictions arising under the Securities Act of 1933 and any
         applicable state securities laws. A copy of such agreement will be
         provided to the holder hereof without charge upon receipt by RCSB
         Financial, Inc. of a written request therefor.

It is understood and agreed that the above legend shall be removed by delivery
of substitute certificate(s) without such legend if COFI shall have delivered to
RCSB an opinion of counsel, in

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form and substance reasonably satisfactory to RCSB and its counsel, to the
effect that such legend is not required for purposes of the Securities Act and
any applicable state securities laws.

         5.       Authorization, etc.
                  ------------------

         (a)      RCSB hereby represents and warrants to COFI that:

                  (i) RCSB has full corporate authority to execute and deliver
         this Option Agreement and, subject to Section 11(i), to consummate the
         transactions contemplated hereby;

                  (ii) such execution, delivery and consummation have been
         authorized by its Board of Directors, and no other corporate actions 
         are necessary therefor; 

                  (iii) this Option Agreement has been duly and validly 
         executed and delivered and represents a valid and legally binding 
         obligation of RCSB, enforceable against RCSB in accordance with its 
         terms; and

                  (iv) RCSB has taken all necessary corporate action to
         authorize and reserve and, subject to Section 11(i), permit it to issue
         and, at all times from the date hereof through the date of the exercise
         in full or the expiration or termination of the Option, shall have
         reserved for issuance upon exercise of the Option, 2,880,944 shares of
         RCSB Common Stock, all of which, upon issuance pursuant hereto, shall
         be duly authorized, validly issued, fully paid and nonassessable, and
         shall be delivered free and clear of all claims, liens, encumbrances,
         restrictions (other than federal and state securities restrictions) and
         security interests and not subject to any preemptive rights.

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         (b)      COFI hereby represents and warrants to RCSB that:

                  (i) COFI has full corporate authority to execute and deliver
         this Option Agreement and, subject to Section 11(i), to consummate the
         transactions contemplated hereby;

                  (ii) such execution, delivery and consummation have been
         authorized by all requisite corporate action by COFI, and no other
         corporate proceedings are necessary therefor;

                  (iii) this Option Agreement has been duly and validly executed
         and delivered and represents a valid and legally binding obligation of
         COFI, enforceable against COFI in accordance with its terms; and

                  (iv) any RCSB Common Stock or other securities acquired by
         COFI upon exercise of the Option will not be taken with a view to the
         public distribution thereof and will not be transferred or otherwise
         disposed of except in compliance with the Securities Act.

         6.       Adjustment upon Changes in Capitalization.
                  -----------------------------------------

         In the event of any change in RCSB Common Stock by reason of dividends,
split-ups, recapitalizations or the like, the type and number of shares subject
to the Option, and the purchase price per share, as the case may be, shall be
adjusted appropriately. In the event that any additional shares of RCSB Common
Stock are issued after the date of this Option Agreement (other than pursuant to
an event described in the preceding sentence or pursuant to this Option
Agreement), the number of shares of RCSB Common Stock subject to the Option
shall be adjusted so that, after such issuance, it equals at least 19.9% of the
number of shares of RCSB Common Stock then issued and outstanding (without
considering any shares subject to or issued pursuant to the Option).

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         7.       Repurchase.
                  ----------

         (a) Subject to Section 11(i), at the request of COFI at any time
commencing upon the occurrence of a Purchase Event and ending 13 months
immediately thereafter (the "Repurchase Period"), RCSB (or any successor entity
thereof) shall repurchase the Option from COFI together with all (but not less
than all, subject to Section 10) shares of RCSB Common Stock purchased by COFI
pursuant thereto with respect to which COFI then has Beneficial Ownership, at a
price (per share, the "Per share Repurchase Price") equal to the sum of:

                  (i)  The exercise price paid by COFI for any shares of RCSB 
         Common Stock acquired pursuant to the Option;

                  (ii) The difference between (A) the "Market/Tender Offer
         Price" for shares of RCSB Common Stock (defined as the higher of (x)
         the highest price per share at which a tender or exchange offer has
         been made for shares of RCSB Common Stock or (y) the highest closing
         mean of the "bid" and the "ask" price per share of RCSB Common Stock
         reported by the Nasdaq, the automated quotation system of the National
         Association of Securities Dealers, Inc., for any day within that
         portion of the Repurchase Period which precedes the date COFI gives
         notice of the required repurchase under this Section 7) and (B) the
         exercise price as determined pursuant to Section 2 hereof (subject to
         adjustment as provided in Section 6), multiplied by the number of
         shares of RCSB Common Stock with respect to which the Option has not
         been exercised, but only if the Market/Tender Offer Price is greater
         than such exercise price; and

                  (iii) The difference between the Market/Tender Offer Price and
         the exercise price paid by COFI for any shares of RCSB Common Stock
         purchased pursuant to the exercise of

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         the Option, multiplied by the number of shares so purchased, but only
         if the Market/Tender Offer Price is greater than such exercise price.

         (b)      In the event COFI exercises its rights under this Section 7, 
RCSB shall, within ten business days thereafter, pay the required amount to COFI
by wire transfer of immediately available funds to an account designated by COFI
and COFI shall surrender to RCSB the Option and the certificates evidencing the
shares of RCSB Common Stock purchased thereunder with respect to which COFI then
has Beneficial Ownership, and COFI shall warrant that it has sole record and
Beneficial Ownership of such certificates and that the same are free and clear
of all liens, claims, charges, restrictions and encumbrances of any kind
whatsoever.

         (c) In determining the Market/Tender Offer Price, the value of any
consideration other than cash shall be determined by an independent nationally
recognized investment banking firm selected by COFI and reasonably acceptable to
RCSB.

         8.       Repurchase at Option of RCSB and First Refusal.
                  ----------------------------------------------

         (a) Except to the extent that COFI shall have previously exercised its
rights under Section 7, at the request of RCSB during the six-month period
commencing 13 months following the first occurrence of a Purchase Event, RCSB
may repurchase from COFI, and COFI shall sell to RCSB, all (but not less than
all, subject to Section 10) of the RCSB Common Stock acquired by COFI pursuant
hereto and with respect to which COFI has Beneficial Ownership at the time of
such repurchase at a price per share equal to the greater of (i) 110% of the
Market/Tender Offer Price per share, (ii) the Per Share Repurchase Price or
(iii) the sum of (A) the aggregate Purchase Price of the shares so repurchased
plus (B) interest on the aggregate Purchase Price paid for the shares so
repurchased from the date of purchase to the date of repurchase at the highest
rate of interest announced by COFI Bank as its prime or base lending or
reference rate during such period, less any

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dividends received on the shares so repurchased, plus (C) COFI's reasonable
out-of-pocket expenses incurred in connection with the transactions contemplated
by the Merger Agreement, including, without limitation, legal, accounting and
investment banking fees. Any repurchase under this Section 8(a) shall be
consummated in accordance with Section 7(b).

         (b) If, at any time after the occurrence of a Purchase Event and prior
to the earlier of (i) the expiration of 18 months immediately following such
Purchase Event or (ii) the expiration or termination of the Option, COFI shall
desire to sell, assign, transfer or otherwise dispose of the Option or all or
any of the shares of RCSB Common Stock acquired by it pursuant to the Option, it
shall give RCSB written notice of the proposed transaction (an "Offeror's
Notice"), identifying the proposed transferee, and setting forth the terms of
the proposed transaction. An Offeror's Notice shall be deemed an offer by COFI
to RCSB, which may be accepted within five business days of the receipt of such
Offeror's Notice, on the same terms and conditions and at the same price at
which COFI is proposing to transfer the Option or such shares to a third party.
The purchase of the Option or any such shares by RCSB shall be closed within
five business days of the date of the acceptance of the offer and the purchase
price shall be paid to COFI by wire transfer of immediately available funds to
an account designated by COFI. In the event of the failure or refusal of RCSB to
purchase the Option or all the shares covered by the Offeror's Notice or if any
regulatory authority disapproves RCSB's proposed purchase of the Option or such
shares, COFI may, within 60 days from the date of the Offeror's Notice, sell
all, but not less than all, of the Option or such shares to such third party at
no less than the price specified and on terms no more favorable to the purchaser
than those set forth in the Offeror's Notice. The requirements of this Section
8(b) shall not apply to (i) any disposition as a result of which the proposed
transferee would Beneficially Own not more than 2%

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of the voting power of RCSB or (ii) any disposition of RCSB Common Stock by a
person to whom COFI has sold RCSB Common Stock issued upon exercise of the
Option.

         9.       Registration Rights.
                  -------------------

         At any time after a Purchase Event, RCSB shall, if requested by any
holder or beneficial owner of shares of RCSB Common Stock issued upon exercise
of the Option (except any beneficial holder who acquired all of such holder's
shares in a transaction exempt from the requirements of Section 8(b) by reason
of clause (i) thereof) (each a "Holder"), as expeditiously as possible file a
registration statement on a form for general use under the Securities Act if
necessary in order to permit the sale or other disposition of the shares of RCSB
Common Stock that have been acquired upon exercise of the Option in accordance
with the intended method of sale or other disposition requested by any such
Holder (it being understood and agreed that any such sale or other disposition
shall be effected on a widely distributed basis so that, upon consummation
thereof, no purchaser or transferee shall Beneficially Own more than 2% of the
shares of RCSB Common Stock then outstanding). Each such Holder shall provide
all information reasonably requested by RCSB for inclusion in any registration
statement to be filed hereunder. RCSB shall use its 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 as may be reasonably necessary to effect such
sales or other dispositions. The registration effected under this Section 9
shall be at RCSB's expense except for underwriting commissions and the fees and
disbursements of such Holders' counsel attributable to the registration of such
RCSB Common Stock. In no event shall RCSB be required to effect more than one
registration hereunder. The filing of the registration statement hereunder may
be delayed for such period of time as may reasonably be required to facilitate
any public distribution by RCSB of RCSB Common Stock or if a special

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audit of RCSB would otherwise be required in connection therewith. If requested
by any such Holder in connection with such registration, RCSB shall become a
party to any underwriting agreement relating to the sale of such certificates,
but only to the extent of obligating itself in respect of representations,
warranties, indemnities and other agreements customarily included in such
underwriting agreements for parties similarly situated. Upon receiving any
request for registration under this Section 9 from any Holder, RCSB agrees to
send a copy thereof to any other person known to RCSB to be entitled to
registration rights under this Section 9, in each case by promptly mailing the
same, postage prepaid, to the address of record of the persons entitled to
receive such copies.

         10.      Severability.
                  ------------

         Any term, provision, covenant or restriction contained in this Option
Agreement held by a court or a regulatory authority of competent jurisdiction to
be invalid, void or unenforceable, shall be ineffective to the extent of such
invalidity, voidness or unenforceability, but neither the remaining terms,
provisions, covenants or restrictions contained in this Option Agreement nor the
validity or enforceability thereof in any other jurisdiction shall be affected
or impaired thereby. Any term, provision, covenant or restriction contained in
this Option Agreement that is so found to be so broad as to be unenforceable
shall be interpreted to be as broad as is enforceable. If for any reason such
court or regulatory authority determines that applicable law will not permit
COFI or any other person to acquire, or RCSB to repurchase or purchase, the full
number of shares of RCSB Common Stock provided in Section 2 hereof (as adjusted
pursuant to Section 6 hereof), it is the express intention of the parties hereto
to allow COFI or such other person to acquire, or RCSB to repurchase or
purchase, such lesser number of shares as may be permissible, without any
amendment or modification hereof.

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         11.      Miscellaneous.
                  -------------

         (a) EXPENSES. Each of the parties hereto shall 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, except as otherwise
provided herein.

         (b) ENTIRE AGREEMENT. Except as otherwise expressly provided herein,
this Option Agreement and the Merger Agreement contain the entire agreement
between the parties with respect to the transactions contemplated hereunder and
supersedes all prior arrangements or understandings with respect thereto,
written or oral.

         (c) SUCCESSORS; NO THIRD PARTY BENEFICIARIES. The terms and conditions
of this Option Agreement shall inure to the benefit of and be binding upon the
parties hereto and their respective successors and permitted assigns. Nothing in
this Option Agreement, expressed or implied, is intended to confer upon any
party, other than the parties hereto, and their respective successors and
assigns, any rights, remedies, obligations, or liabilities under or by reason of
this Option Agreement, except as expressly provided herein.

         (d) ASSIGNMENT. Other than as provided in Sections 8 and 9 hereof,
neither of the parties hereto may sell, transfer, assign or otherwise dispose of
any of its rights or obligations under this Option Agreement or the Option
created hereunder to any other person (whether by operation of law or
otherwise), without the express written consent of the other party.

         (e) NOTICES. All notices or other communications which are required or
permitted hereunder shall be in writing and sufficient if delivered in
accordance with Section 8.2 of the Merger Agreement (which is incorporated
herein by reference).

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         (f) COUNTERPARTS. This Option Agreement may be executed in
counterparts, and each such counterpart shall be deemed to be an original
instrument, but both such counterparts together shall constitute but one
agreement.

         (g) SPECIFIC PERFORMANCE. The parties hereto agree that if for any
reason COFI or RCSB shall have failed to perform its obligations under this
Option Agreement, then either party hereto seeking to enforce this Option
Agreement against such non-performing party shall be entitled to specific
performance and injunctive and other equitable relief, and the parties hereto
further agree to waive any requirement for the securing or posting of any bond
in connection with the obtaining of any such injunctive or other equitable
relief. This provision is without prejudice to any other rights that either
party hereto may have against the other party hereto for any failure to perform
its obligations under this Option Agreement.

         (h) GOVERNING LAW. This Option Agreement shall be governed by and
construed in accordance with the laws of the State of Delaware applicable to
agreements made and entirely to be performed within such state. Nothing in this
Option Agreement shall be construed to require any party (or any subsidiary or
affiliate of any party) to take any action or fail to take any action in
violation of applicable law, rule or regulation.

         (i) REGULATORY APPROVALS; SECTION 16(b). If, in connection with (A) the
exercise of the Option under Section 3 or a sale by COFI to a third party under
Section 8, (B) a repurchase by RCSB under Section 7 or a repurchase or purchase
by RCSB under Section 8, prior notification to or approval of the OTS or any
other regulatory authority is required, then the required notice or application
for approval shall be promptly filed and expeditiously processed and periods of
time that otherwise would run pursuant to such Sections shall run instead from
the date on which any such required notification period has expired or been
terminated or such approval has been obtained, and

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in either event, any requisite waiting period shall have passed. In the case of
clause (A) of this subsection (i), such filing shall be made by COFI, and in the
case of clause (B) of this subsection (i), such filing shall be made by RCSB,
provided that each of COFI and RCSB shall use its best efforts to make all
filings with, and to obtain consents of, all third parties and Regulatory
Authorities necessary to the consummation of the transactions contemplated
hereby. Periods of time that otherwise would run pursuant to Sections 3, 7 or 8
shall also be extended to the extent necessary to avoid liability under Section
16(b) of the Exchange Act.

         (j) NO BREACH OF AGREEMENT AUTHORIZED.  Nothing contained in this 
Option Agreement shall be deemed to authorize RCSB to issue any shares of RCSB
Common Stock in breach of, or otherwise breach any of, the provisions of the
Merger Agreement.

         (k) WAIVER AND AMENDMENT. Any provision of this Agreement may be waived
at any time by the party that is entitled to the benefits of such provision.
This Option Agreement may not be modified, amended, altered or supplemented
except upon the execution and delivery of a written agreement executed by the
parties hereto.

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         Each of the parties hereto has executed this Option Agreement as of the
date first written above.


                                            CHARTER ONE FINANCIAL, INC.

                                            By:  /s/  Charles J. Koch
                                               _____________________________
                                               Name:    Charles J. Koch
                                               Title:   Chief Executive Officer


                                            RCSB FINANCIAL, INC.

                                            By:  /s/  Leonard S. Simon
                                               _____________________________
                                               Name:  Leonard S. Simon
                                               Title: Chief Executive Officer

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