<Page>

                                                                   Exhibit 4.2

<Table>
<Caption>
<S>                                          <C>                                        <C>
NUMBER
KPD

                                                            KEYSTONE                                     SHARES
                                                         PROPERTY TRUST

THIS CERTIFICATE IS TRANSFERABLE IN           A REAL ESTATE INVESTMENT TRUST ORGANIZED                CUSIP 493596 30 8
        NEW YORK, N.Y.                         UNDER THE LAWS OF THE STATE OF MARYLAND

                                                                                           SEE REVERSE FOR GENERAL DEFINITIONS
                                                                                                         AND LEGENDS
</Table>

THIS CERTIFIES THAT:







is the owner of



     FULLY-PAID AND NONASSESSABLE SERIES D PREFERRED SHARES, $.001 PAR VALUE, OF
                            KEYSTONE PROPERTY TRUST


Transferable on the books of the Trust by the holder hereof in person or by
duly authorized attorney, upon surrender of this Certificate properly
endorsed. This Certificate and the shares represented hereby are issued and
shall be held subject to all the provisions of the Declaration of Trust, as
amended or supplemented, and the By-Laws of the Trust, as amended (copies of
which are on file at the office of the Transfer Agent), to all of which the
holder of this Certificate by acceptance hereof assents. This Certificate is
not valid unless countersigned and registered by the Transfer Agent and
Registrar.

     WITNESS the facsimile seal of the Trust and the facsimile signatures of
its duly authorized officers.

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<Caption>
<S>                      <C>                                  <C>
Dated:

                          KEYSTONE PROPERTY TRUST
  /s/ Saul A. Behar               SEAL                         /s/ Jeffrey E. Kelter
                                  1999
      Secretary                 MARYLAND                       President and Chief Executive Officer
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                                       COUNTERSIGNED AND REGISTERED:
                                       AMERICAN STOCK TRANSFER & TRUST COMPANY
                                                     (NEW YORK, NEW YORK)
                                                                TRANSFER AGENT
                                                                 AND REGISTRAR

                                       BY

                                                             AUTHORIZED OFFICER



<Page>

     The Trust will furnish to any Shareholder on request and without charge
a full statement of the designations and any preferences, conversion and
other rights, voting powers, restrictions, limitations as to dividends or
distributions, qualifications, and terms and conditions of redemption of the
shares of each class which the Trust is authorized to issue, of the
differences in the relative rights and preferences between the shares of each
series of a preferred or special class in series which the Trust is
authorized to issue, to the extent they have been set, and of the
authority of the Board of Trustees to set the relative rights and
preferences of subsequent series of a preferred or special class of shares.
Such request may be made to the secretary of the Trust or to its transfer
agent.

     The securities represented by this certificate are subject to
restrictions on Beneficial and Constructive Ownership and Transfer for the
purpose of the Trust's maintenance of its status as a Real Estate Investment
Trust under the Internal Revenue Code of 1986, as amended (the "Code").
Subject to certain further restrictions and except as expressly provided in
the Trust's Declaration of Trust, (i) no Person may Beneficially or
Constructively Own Common Shares of the Trust in excess of 4.9% (in value or
number of shares) of the outstanding Common Shares of the Trust unless such
Person is an Exempted Holder (in which case the Excepted Holder Ownership
Limit shall be applicable); (ii) no Person may Beneficially or Constructively
Own Shares of the Trust in excess of 9.9% (in value or number of shares) of
the outstanding Shares of any class or series of Preferred Stock of the
Trust, unless such Person is an Excepted Holder (in which case the Excepted
Holder Ownership Limit shall be applicable); (iii) no Person may Beneficially
or Constructively Own Shares that would result in the Trust being "closely
held" under Section 856(h) of the Code or otherwise cause the Trust to fail
to qualify as a REIT; (iv) no Person may Transfer Shares if such transfer
would result in the Shares of the Trust being owned by fewer than 100
Persons; (v) no Person may transfer Shares if such Transfer would result in
Shares of the Trust being owned by a Disqualified Person; and (vi) no plans
and certain other Persons described in or subject to the Plan Asset
Regulations may own more than 24.9% of the value of any class of Shares of
the Trust. Any Person who Beneficially or Constructively Owns or attempts to
Beneficially or Constructively Own Shares which causes or will cause a Person
to Beneficially or Constructively Own Shares in excess or in violation of the
above limitations must immediately notify the Trust. If any of the
restrictions on transfer or ownership are violated, the Shares represented
hereby may be automatically transferred to a Charitable Trustee of a
Charitable Trust for the benefit of one or more Charitable Beneficiaries. In
addition, upon the occurence of certain events, attempted Transfers in
violation of the restrictions described above may be void AB INITIO. All
capitalized terms in this legend have the meanings defined in the Declaration
of Trust, as the same may be amended or supplemented from time to time, a
copy of which, including the restrictions on transfer and ownership, will be
furnished to each holder of Shares of the Trust on request and without charge.

     Keep this certificate in a safe place. If it is lost, stolen, or
destroyed, the Trust will require a bond of indemnity as a condition to the
issuance of a replacement certificate.

     The following abbreviations, when used in the inscription on the face of
this certificate, shall be construed as though they were written out in full
according to applicable laws or regulations:

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<S><C>
TEN COM     --      as tenants in common                       UNIF GIFT MIN ACT--            Custodian
                                                                                   ----------          ------------
                                                                                      (Cust)              (Minor)
TEN ENT     --      as tenants by the entireties                                     under Uniform Gifts to Minors
                                                                                   Act
                                                                                      ------------------------------
                                                                                                   (State)
JT TEN      --      as joint tenants with right of
                    survivorship and not as tenants in common

    Additional abbreviations may also be used though not in the above list.

    For value received, _____________________ hereby sell, assign and
transfer unto

   PLEASE INSERT SOCIAL SECURITY OR OTHER
       IDENTIFYING NUMBER OF ASSIGNEE
-------------------------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
Please print or typewrite name and address including postal zip code of assignee

--------------------------------------------------------------------------------

---------------------------------------------------------------Preferred Shares

represented by the within Certificate, and do hereby irrevocably constitute
and appoint

--------------------------------------------------------------------------------
Attorney to transfer the said shares on the books of the within-named Trust with
full power of substitution in the premises.
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Dated
      --------------------------

                                           ----------------------------------
                                                        SIGNATURE

Signature Guaranteed:


By:
  ---------------------------------------------------------------------------
The signature(s) must be guaranteed by an Eligible Guarantor Institution
(Banks, Stockbrokers, Savings and Loan Associations and Credit Unions with
membership in an approved signature guarantee Medallion Program), pursuant
to S.E.C. Rule 17Ad-15.


NOTICE: The signature in this assignment must correspond with the name as
written upon the face of the Certificate, in every particular, without
alteration or enlargement, or any change whatever.