Exhibit 4.3

[FRONT OF STOCK CERTIFICATE]

RESTRICTED SECURITIES                                SEE LEGENDS ON REVERSE SIDE

                                State of Maryland

                  0                                           0

                        Franklin Street Properties Corp.
          FULLY                                                   NON-ASSESSABLE
                                  Common Stock

                           $.0001 Par Value Per Share

                                                Specimen
                       of Franklin Street Properties Corp.

          President                                            Treasurer
<PAGE>

[REVERSE OF STOCK CERTIFICATE]

      The shares represented by this certificate have not been registered under
the Securities Act of 1933, as amended, and may not be transferred, pledged or
hypothecated unless and until such shares are registered under such Act or an
opinion of counsel satisfactory to the Company is obtained to the effect that
such registration is not required.

      The Corporation is authorized to issue capital stock of more than one
class, consisting of Common Shares and one or more classes of Preferred Shares.
The Board of Directors is authorized to determine the preferences, limitations
and relative rights of any class of Preferred Shares before the issuance of any
such Preferred Shares, or any class thereof. The Corporation will furnish,
without charge, to any shareholder making a written request therefor, a written
statement of the designations, relative rights, preferences, conversion and
other rights, voting powers, restrictions, limitations as to dividends,
qualifications and terms and conditions of redemption applicable to each class
of shares. Requests for such written statement may be directed to the Secretary
of the Corporation at the principal office of the Corporation.

      The shares represented by this certificate are subject to restrictions on
Beneficial Ownership, Constructive Ownership and Transfer for the purpose of the
Corporation's maintenance of its status as a "real estate investment trust" (a
"REIT") under the Internal Revenue Code of 1986, as amended, or any successor
statute (the "Code"). Subject to certain further restrictions, and except as
expressly provided in the Corporation's Charter, (i) no Person may Beneficially
Own or Constructively Own shares of the Corporation's Common Shares or Preferred
Shares in excess of 9.8% in value or number of shares (whichever is more
restrictive) of the outstanding Common Shares or Preferred Shares, respectively,
of the Corporation, (ii) no Person may Transfer or Acquire Equity Shares if such
Transfer or Acquisition would result in the Corporation being owned by fewer
than 100 Persons and (iii) no Person may Beneficially Own or Constructively Own
Equity Shares that would result in the Corporation being "closely held" under
Section 856(h) of the Code or otherwise cause the Corporation to fail to qualify
as a REIT. Any Person who Beneficially Owns or Constructively Owns or attempts
to Beneficially or Constructively Own Equity Shares which causes or will cause a
Person to Beneficially Own or Constructively Own Equity Shares in violation of
the above restrictions must immediately notify the Corporation. If some or all
of the restrictions on transfer or ownership set forth in clauses (i) or (iii)
are violated by a purported Transfer of the Equity Shares represented hereby,
the Equity Shares represented hereby will be automatically transferred to a
Trustee of a Trust for the benefit of one or more Charitable Beneficiaries. In
addition, the Corporation may redeem Equity Shares represented hereby if a
purported Transfer violates the restrictions described above. Furthermore,
attempted Transfers in violation of the restrictions described above may be void
ab initio. A Person who attempts to Beneficially or Constructively Own Equity
Shares in violation of the restrictions described above shall have no claim,
cause of action or any recourse whatsoever against a transferor of such Equity
Shares. All capitalized terms in this legend have the meanings defined in the
Charter of the Corporation, as the same may be amended from time to time, a copy
of which, including the restrictions on transfer and ownership, will be
furnished, without charge, to each holder of Equity Shares who directs a request
to the Secretary of the Corporation at the principal office of the Corporation.