<PAGE>
                                                                               .
                                                                               .
                                                                               .
                                    KEYSTONE
                                 PROPERTY TRUST
         NUMBER                                             SHARES
       KPE

<Table>
<S>                                        <C>                                                 <C>
                                                                                                      CUSIP 493596 40 7
THIS CERTIFICATE IS TRANSFERABLE IN        A Real Estate Investment Trust organized under
        NEW YORK, N.Y.                         the laws of the State of Maryland               SEE REVERSE FOR CERTAIN DEFINITIONS
                                                                                                           AND LEGENDS
</Table>

THIS CERTIFIES THAT








is the owner of

  FULLY-PAID AND NONASSESSABLE 7.375% SERIES E CUMULATIVE REDEEMABLE PREFERRED
                           STOCK, $.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 at
the office of the Transfer Agent), to all of which the holder of this
Certificate by acceptance thereof assents. This Certificate is not valid unless
signed and registered by the Transfer Agent and Registrar.

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

Dated:
                  [KEYSTONE PROPERTY TRUST SEAL 1999 MARYLAND]

/s/ Saul A. Behar                                 /s/ Jeffrey E. Kelter

               Secretary                   President and Chief Executive 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 difference
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 9.8% (in value or number of shares) of the outstanding
Common Shares of the Trust unless such Person is an Excepted 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 the
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 that 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 occurrence of certain
events, attempted Transfers in violation of the restrictions described above may
be void ab truitio. 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:

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

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


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

[NOTICE: THE SIGNATURE TO 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.]

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.

Dated _________________________________


                                        ________________________________________
                                                        SIGNATURE


Signature Guaranteed


By:_____________________________________________________________________________
   THE SIGNATURE(S) MUST BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION
   (BANKS, STOCKHOLDERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH
   MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE MEDALLION PROGRAM), PURSUANT TO
   S.E.C. RULE 17AD-18.