UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                  SCHEDULE 13G
                                (RULE 13d - 102)

             Information to be included in statements filed pursuant
           to Rules 13d-1(b), (c) and (d) and amendments thereto filed
                              pursuant to 13d-2(b)

                              (AMENDMENT NO.___ )*

                             Keystone Property Trust
                                (Name of Issuer)

                          Common Stock, par value $.001
                         (Title of Class of Securities)

                                    493596100
                                 (CUSIP Number)


                                  May 14, 2004
             (Date of Event which Requires Filing of this Statement)

                 Check the appropriate box to designate the rule
                    pursuant to which this Schedule is filed:

                                [ ] Rule 13d-1(b)
                                [x] Rule 13d-1(c)
                                [ ] Rule 13d-1(d)


     *The  remainder  of this cover  page  shall be filled  out for a  reporting
person's  initial  filing on this  form with  respect  to the  subject  class of
securities,  and for any subsequent amendment containing information which would
alter disclosures provided in a prior cover page.

     The  information  required on the remainder of this cover page shall not be
deemed to be "filed"  for the purpose of Section 18 of the  Securities  Exchange
Act of 1934 ("Act") or otherwise  subject to the  liabilities of that section of
the Act but shall be subject to all other  provisions of the Act  (however,  see
the Notes).

                       (Continued on the Following Pages)




1.      NAMES OF REPORTING PERSONS
        I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

               Castlerigg Master Investments Ltd.

2.      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

        (a)  [x]
        (b)  [ ]

3.      SEC USE ONLY

4.      CITIZENSHIP OR PLACE OF ORGANIZATION

             British Virgin Islands

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:

5.      SOLE VOTING POWER

             0

6.      SHARED VOTING POWER

             2,680,500

7.      SOLE DISPOSITIVE POWER

             0

8.      SHARED DISPOSITIVE POWER

             2,680,500

9.      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

             2,680,500

10.     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9)
        EXCLUDES CERTAIN SHARES*       [X]

11.     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

             8.7%

12.     TYPE OF REPORTING PERSON*

             CO

                      *SEE INSTRUCTIONS BEFORE FILLING OUT!



1.      NAMES OF REPORTING PERSONS
        I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

             Sandell Asset Management Corp.

2.      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

        (a)  [x]
        (b)  [ ]

3.      SEC USE ONLY

4.      CITIZENSHIP OR PLACE OF ORGANIZATION

             British Virgin Islands

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:

5.      SOLE VOTING POWER

             0

6.      SHARED VOTING POWER

             2,680,500

7.      SOLE DISPOSITIVE POWER

             0

8.      SHARED DISPOSITIVE POWER

             2,680,500

9.      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

             2,680,500

10.     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9)
        EXCLUDES CERTAIN SHARES*       [X]

11.     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

             8.7%

12.     TYPE OF REPORTING PERSON*

             CO

                      *SEE INSTRUCTIONS BEFORE FILLING OUT!


1.      NAMES OF REPORTING PERSONS
        I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

               Castlerigg International Limited

2.      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

        (a)  [x]
        (b)  [ ]

3.      SEC USE ONLY

4.      CITIZENSHIP OR PLACE OF ORGANIZATION

             British Virgin Islands

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:

5.      SOLE VOTING POWER

             0

6.      SHARED VOTING POWER

             2,680,500

7.      SOLE DISPOSITIVE POWER

             0

8.      SHARED DISPOSITIVE POWER

             2,680,500

9.      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

             2,680,500

10.     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9)
        EXCLUDES CERTAIN SHARES*       [X]

11.     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

             8.7%

12.     TYPE OF REPORTING PERSON*

             CO

                      *SEE INSTRUCTIONS BEFORE FILLING OUT!


1.      NAMES OF REPORTING PERSONS
        I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

               Castlerigg International Holdings Limited

2.      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

        (a)  [x]
        (b)  [ ]

3.      SEC USE ONLY

4.      CITIZENSHIP OR PLACE OF ORGANIZATION

             British Virgin Islands

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:

5.      SOLE VOTING POWER

             0

6.      SHARED VOTING POWER

             2,680,500

7.      SOLE DISPOSITIVE POWER

             0

8.      SHARED DISPOSITIVE POWER

             2,680,500

9.      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

             2,680,500

10.     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9)
        EXCLUDES CERTAIN SHARES*       [X]

11.     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

             8.7%

12.     TYPE OF REPORTING PERSON*

             CO

                      *SEE INSTRUCTIONS BEFORE FILLING OUT!


1.      NAMES OF REPORTING PERSONS
        I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

             Thomas E. Sandell

2.      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

        (a)  [x]
        (b)  [ ]

3.      SEC USE ONLY

4.      CITIZENSHIP OR PLACE OF ORGANIZATION

             Sweden

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:

5.      SOLE VOTING POWER

             0

6.      SHARED VOTING POWER

             2,680,500

7.      SOLE DISPOSITIVE POWER

             0

8.      SHARED DISPOSITIVE POWER

             2,680,500

9.      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

             2,680,500

10.     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9)
        EXCLUDES CERTAIN SHARES*       [X]

11.     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

             8.7%

12.     TYPE OF REPORTING PERSON*

             IN

                      *SEE INSTRUCTIONS BEFORE FILLING OUT!


ITEM 1(a).      NAME OF ISSUER:

     Keystone Property Trust ("Issuer")

ITEM 1(b).      ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES:

     200 Four Falls Suite 208
     West Conshohocken, Pennsylvania 19428


ITEM 2(a).      NAME OF PERSON FILING:

     The  names of the  persons  filing  this  statement  on  Schedule  13G are:
Castlerigg   Master   Investments   Ltd.,  a  British  Virgin  Islands   company
("Castlerigg  Master  Investments"),  Sandell Asset Management  Corp., a British
Virgin Islands company ("SAMC"),  Castlerigg  International  Limited,  a British
Virgin Islands company ("Castlerigg  International"),  Castlerigg  International
Holdings Limited, a British Virgin Islands company ("Castlerigg Holdings"),  and
Thomas E. Sandell, a citizen of Sweden ("Sandell").

ITEM 2(b).      ADDRESS OF PRINCIPAL BUSINESS OFFICE OR, IF NONE, RESIDENCE:

     The principal  business address for each of Castlerigg Master  Investments,
Castlerigg  International  and  Castlerigg  Holdings is c/o Citco Fund  Services
(Curacao) N.V., Kaya Flamboyan 9, P.O. Box 812, Curacao, Netherlands, Antilles.

     The principal  business address for each of SAMC and Sandell is 1251 Avenue
of the Americas, 23rd Floor, New York, New York 10020.

ITEM 2(c).      CITIZENSHIP:

     Each of Castlerigg Master Investments, Castlerigg International, Castlerigg
Holdings  and SAMC is a  company  formed  under the laws of the  British  Virgin
Islands.

     Mr. Sandell is a citizen of Sweden.

ITEM 2(d).      TITLE OF CLASS OF SECURITIES:

     Common Stock, par value $.001 per share (the "Common Stock")

ITEM 2(e).      CUSIP NUMBER:

     493596100


ITEM 3.         IF THIS STATEMENT IS FILED PURSUANT TO RULE 13d-1(b),
                OR 13d-2(b) OR (c), CHECK WHETHER THE PERSON FILING IS A:

        (a)     [ ] Broker or dealer registered under Section 15 of the
                    Exchange Act.

        (b)     [ ] Bank as defined in Section 3(a)(6) of the Exchange Act.

        (c)     [ ] Insurance company defined in Section 3(a)(19) of the
                    Exchange Act.


        (d)     [ ] Investment company registered under Section 8 of the
                    Investment Company Act.

        (e)     [ ] An investment adviser in accordance with Rule
                    13d-1(b)(1)(ii)(E).

        (f)     [ ] An employee benefit plan or endowment fund in accordance
                    with Rule 13d-1(b)(1)(ii)(F).

        (g)     [ ] A parent holding company or control person in accordance
                    with Rule 13d-1(b)(1)(ii)(G).

        (h)     [ ] A savings association as defined in Section 3(b) of the
                    Federal Deposit Insurance Act.

        (i)     [ ] A church plan that is excluded from the definition of an
                    investment company under Section 3(c)(14) of the
                    Investment Company Act;

        (j)     [ ] Group, in accordance with Rule 13d-1(b)(1)(ii)(J).

   If this statement is filed pursuant to Rule 13d-1(c), check this box [x]

ITEM 4.         OWNERSHIP.

     Provide  the  following  information  regarding  the  aggregate  number and
percentage of the class of securities of the issuer identified in Item 1.

         (a)      Amount beneficially owned:

                  The Reporting  Persons  beneficially own 2,680,500 shares of
                  Common Stock.


         (b)      Percent of Class:

                  The Reporting  Persons  beneficially own 2,680,500 shares of
                  Common Stock representing 8.7% of all the outstanding shares
                  of Common Stock.

         (c)      Number of shares as to which such person has:

                  (i)   Sole power to vote or to direct the vote

                        Not applicable.

                  (ii)  Shared power to vote or to direct the vote of shares
                        of Common Stock:

                        Castlerigg Master Investments, Castlerigg International,
                        Castlerigg Holdings, SAMC and Mr. Sandell have the
                        shared power to vote or  direct  the vote of  2,680,500
                        shares of Common Stock beneficially owned by the
                        Reporting Persons.

                  (iii) Sole power to dispose or to direct the disposition of
                        shares of Common Stock:

                        Not applicable.


                  (iv)  Shared power to dispose or to direct the disposition of
                        shares of Common Stock:

                        Castlerigg Master Investments, Castlerigg International,
                        Castlerigg Holdings, SAMC and Mr. Sandell have the
                        shared power to dispose or to direct the disposition of
                        the 2,680,500 shares of Common Stock beneficially owned
                        by the Reporting Persons.


ITEM 5.    OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS.

     If this  statement  is being  filed to report  the fact that as of the date
hereof the Reporting Persons have ceased to be the beneficial owner of more than
five percent of the class of securities, check the following [ ].


ITEM 6.    OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER
           PERSON.

     Not applicable.


ITEM 7.    IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH
           ACQUIRED THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING
           COMPANY.

     The shares of Common Stock  beneficially owned by the Reporting Persons are
owned  directly by Castlerigg  Master  Investments.  Castlerigg  Holdings is the
controlling   shareholder  of  Castlerigg  Master   Investments  and  Castlerigg
International is the controlling shareholder of Castlerigg Holdings.

ITEM 8.    IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP.

     See Exhibit B attached hereto.


ITEM 9.    NOTICE OF DISSOLUTION OF GROUP.

     Not applicable.


ITEM 10.   CERTIFICATION.

     By signing below the undersigned  certifies that, to the best of its or his
knowledge and belief, the securities referred to above were not acquired and are
not held for the purpose of or with the effect of changing  or  influencing  the
control of the issuer of the  securities  and were not acquired and are not held
in connection with or as a participant in any transaction having that purpose or
effect.


                                    SIGNATURE

        After reasonable inquiry and to the best of its knowledge and belief,
the undersigned certifies that the information set forth in this statement is
true, complete, and correct.


Dated:  June 28, 2004      CASTLERIGG MASTER INVESTMENTS LTD.
                           By: Sandell Asset Management Corp.
                                As Investment Manager


                               By: /s/ Thomas E. Sandell
                                   ---------------------
                               Name:   Thomas E. Sandell
                               Title:  Director


                           SANDELL ASSET MANAGEMENT CORP.


                           By: /s/ Thomas E. Sandell
                               ---------------------
                           Name:   Thomas E. Sandell
                           Title:  Director



                           CASTLERIGG INTERNATIONAL LIMITED


                           By: /s/ Thomas E. Sandell
                               ---------------------
                           Name:   Thomas E. Sandell
                           Title:  Director


                           CASTLERIGG INTERNATIONAL HOLDINGS LIMITED


                           By: /s/ Thomas E. Sandell
                               ---------------------
                           Name:   Thomas E. Sandell
                           Title:  Director


                           /s/ Thomas E. Sandell
                           ---------------------
                               Thomas E. Sandell




                                    EXHIBIT A
                             JOINT FILING AGREEMENT

     The  undersigned  hereby  agree that the  statement  on  Schedule  13G with
respect to the Common Stock of Keystone Property Trust dated as of June 28, 2004
is, and any further  amendments  thereto signed by each of the undersigned shall
be,  filed on behalf of each of the  undersigned  pursuant to and in  accordance
with the provisions of Rule 13d-1(k) under the Securities  Exchange Act of 1934,
as amended.


Dated:  June 28, 2004      CASTLERIGG MASTER INVESTMENTS LTD.
                           By: Sandell Asset Management Corp.
                                As Investment Manager


                               By: /s/ Thomas E. Sandell
                                   ---------------------
                               Name:   Thomas E. Sandell
                               Title:  Director


                           SANDELL ASSET MANAGEMENT CORP.


                           By: /s/ Thomas E. Sandell
                               ---------------------
                           Name:   Thomas E. Sandell
                           Title:  Director



                           CASTLERIGG INTERNATIONAL LIMITED


                           By: /s/ Thomas E. Sandell
                               ---------------------
                           Name:   Thomas E. Sandell
                           Title:  Director


                           CASTLERIGG INTERNATIONAL HOLDINGS LIMITED


                           By: /s/ Thomas E. Sandell
                               ---------------------
                           Name:   Thomas E. Sandell
                           Title:  Director


                           /s/ Thomas E. Sandell
                           ---------------------
                               Thomas E. Sandell



                                    EXHIBIT B

                     IDENTIFICATION OF MEMBERS OF THE GROUP



Castlerigg Master Investments Ltd.
Sandell Asset Management Corp.
Castlerigg International Limited
Castlerigg International Holdings Limited
Thomas E. Sandell