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

                                 SCHEDULE 13D/A
                    Under the Securities Exchange Act of 1934

                                 Amendment No. 4

                                 GSI Group Inc.
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                                (Name of Issuer)

                           Common Stock, no par value
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                         (Title of Class of Securities)

                                    36229U102
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                                 (CUSIP Number)

                                Stephanie S. Chen
                          c/o Tinicum Lantern II L.L.C.
                          800 Third Avenue, 40th Floor
                               New York, NY 10022
                                  212-446-9300

--------------------------------------------------------------------------------
(Name, Address and Telephone Number of Person Authorized to Receive Notices and
                                 Communications)

                                   May 7, 2010
                               ------------------
             (Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report
the acquisition that is the subject of this Schedule 13D, and is filing this
schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box
[ ].

Note: Schedules filed in paper format shall include a signed original and five
copies of the schedule, including all exhibits. See Rule 13d-7 for other parties
to whom copies are to be sent.

--------------------
* 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 following pages)
                               (Page 1 of 8 Pages)





----------------------------                        ----------------------------
CUSIP No.  36229U102            SCHEDULE 13D/A        Page 2 of 8 Pages
----------------------------                        ----------------------------
------------- -----------------------------------------------------------------
     1        NAME OF REPORTING PERSON

              Tinicum Capital Partners II, L.P.
------------- -----------------------------------------------------------------
     2        CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) |_|  (b) |X|

------------- -----------------------------------------------------------------
     3        SEC USE ONLY
------------- -----------------------------------------------------------------
     4        SOURCE OF FUNDS

              WC, OO
------------- -----------------------------------------------------------------
     5        CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
              TO ITEMS 2(d) or 2(e)     |_|
------------- -----------------------------------------------------------------
     6        CITIZENSHIP OR PLACE OF ORGANIZATION

              Delaware
------------- -----------------------------------------------------------------
 NUMBER OF    7           SOLE VOTING POWER

   SHARES                 0
              ----------- -----------------------------------------------------
BENEFICIALLY  8           SHARED VOTING POWER

   OWNED                  418,464
              ----------- -----------------------------------------------------
  BY EACH     9           SOLE DISPOSITIVE POWER

 REPORTING                0
              ----------- -----------------------------------------------------
  PERSON      10          SHARED DISPOSITIVE POWER

                          418,464
------------- ----------- -----------------------------------------------------
     11       AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

              418,464
------------- -----------------------------------------------------------------
     12       CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
              SHARES |_|
------------- -----------------------------------------------------------------
     13       PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11

              0.8% (see Item 4)
------------- -----------------------------------------------------------------
     14       TYPE OF REPORTING PERSON
              PN
------------- -----------------------------------------------------------------





----------------------------                        ----------------------------
CUSIP No.  36229U102            SCHEDULE 13D/A        Page 3 of 8 Pages
----------------------------                        ----------------------------
------------- -----------------------------------------------------------------
     1        NAME OF REPORTING PERSON

              Tinicum Lantern II L.L.C.

------------- -----------------------------------------------------------------
     2        CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) |_|  (b) |X|

------------- -----------------------------------------------------------------
     3        SEC USE ONLY
------------- -----------------------------------------------------------------
     4        SOURCE OF FUNDS

              AF
------------- -----------------------------------------------------------------
     5        CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
              TO ITEMS 2(d) or 2(e)     |_|
------------- -----------------------------------------------------------------
     6        CITIZENSHIP OR PLACE OF ORGANIZATION

              Delaware
------------- -----------------------------------------------------------------
 NUMBER OF    7           SOLE VOTING POWER

   SHARES                 0
              ----------- -----------------------------------------------------
BENEFICIALLY  8           SHARED VOTING POWER

   OWNED                  418,464
              ----------- -----------------------------------------------------
  BY EACH     9           SOLE DISPOSITIVE POWER

 REPORTING                0
              ----------- -----------------------------------------------------
  PERSON      10          SHARED DISPOSITIVE POWER

                          418,464
------------- ----------- -----------------------------------------------------
     11       AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

              418,464
------------- -----------------------------------------------------------------
     12       CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
              SHARES |_|
------------- -----------------------------------------------------------------
     13       PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11

              0.8% (see Item 4)
------------- -----------------------------------------------------------------
     14       TYPE OF REPORTING PERSON
              OO
------------- -----------------------------------------------------------------





----------------------------                        ----------------------------
CUSIP No.  36229U102            SCHEDULE 13D/A        Page 4 of 8 Pages
----------------------------                        ----------------------------
------------- -----------------------------------------------------------------
     1        NAME OF REPORTING PERSON

              Terence M. O'Toole

------------- -----------------------------------------------------------------
     2        CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) |_|  (b) |X|

------------- -----------------------------------------------------------------
     3        SEC USE ONLY
------------- -----------------------------------------------------------------
     4        SOURCE OF FUNDS

              AF
------------- -----------------------------------------------------------------
     5        CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
              TO ITEMS 2(d) or 2(e)     |_|
------------- -----------------------------------------------------------------
     6        CITIZENSHIP OR PLACE OF ORGANIZATION

              United States
------------- -----------------------------------------------------------------
 NUMBER OF    7           SOLE VOTING POWER

   SHARES                 0
              ----------- -----------------------------------------------------
BENEFICIALLY  8           SHARED VOTING POWER

   OWNED                  418,464
              ----------- -----------------------------------------------------
  BY EACH     9           SOLE DISPOSITIVE POWER

 REPORTING                0
              ----------- -----------------------------------------------------
  PERSON      10          SHARED DISPOSITIVE POWER

                          418,464
------------- ----------- -----------------------------------------------------
     11       AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

              418,464
------------- -----------------------------------------------------------------
     12       CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
              SHARES |_|
------------- -----------------------------------------------------------------
     13       PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11

              0.8% (see Item 4)
------------- -----------------------------------------------------------------
     14       TYPE OF REPORTING PERSON
              IN
------------- -----------------------------------------------------------------





----------------------------                        ----------------------------
CUSIP No.  36229U102            SCHEDULE 13D/A        Page 5 of 8 Pages
----------------------------                        ----------------------------
------------- -----------------------------------------------------------------
     1        NAME OF REPORTING PERSON

              Eric M. Ruttenberg

------------- -----------------------------------------------------------------
     2        CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) |_|  (b) |X|

------------- -----------------------------------------------------------------
     3        SEC USE ONLY
------------- -----------------------------------------------------------------
     4        SOURCE OF FUNDS

              AF
------------- -----------------------------------------------------------------
     5        CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
              TO ITEMS 2(d) or 2(e)     |_|
------------- -----------------------------------------------------------------
     6        CITIZENSHIP OR PLACE OF ORGANIZATION

              United States
------------- -----------------------------------------------------------------
 NUMBER OF    7           SOLE VOTING POWER

   SHARES                 0
              ----------- -----------------------------------------------------
BENEFICIALLY  8           SHARED VOTING POWER

   OWNED                  418,464
              ----------- -----------------------------------------------------
  BY EACH     9           SOLE DISPOSITIVE POWER

 REPORTING                0
              ----------- -----------------------------------------------------
  PERSON      10          SHARED DISPOSITIVE POWER

                          418,464
------------- ----------- -----------------------------------------------------
     11       AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

              418,464
------------- -----------------------------------------------------------------
     12       CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
              SHARES |_|
------------- -----------------------------------------------------------------
     13       PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11

              0.8% (see Item 4)
------------- -----------------------------------------------------------------
     14       TYPE OF REPORTING PERSON
              IN
------------- -----------------------------------------------------------------





----------------------------                        -------------------------
CUSIP No.  36229U102            SCHEDULE 13D/A        Page 6 of 8 Pages
----------------------------                        -------------------------
ITEM 1.       SECURITY AND ISSUER

     This Amendment No. 4 (the "Amendment") amends the statement on Schedule 13D
filed on January 13, 2010 (the "Original Schedule 13D", as amended hereby and by
Amendment No. 1 filed on March 3, 2010, Amendment No. 2 filed on March 16, 2010
and Amendment No. 3 filed on March 19, 2010, the "Schedule 13D") with respect to
the common stock, no par value (the "Common Stock"), of GSI Group Inc., a
company continued and existing under the laws of the Province of New Brunswick,
Canada (the "Issuer"). Capitalized terms used herein and not otherwise defined
in this Amendment have the meanings set forth in the Schedule 13D. This
Amendment amends Items 4, 6 and 7 as set forth below.

ITEM 4.       PURPOSE OF TRANSACTION

Item 4 of the Schedule 13D is hereby amended and supplemented by the addition of
the following:

On May 7, 2010 TCP II and the other Consenting Noteholders reached an agreement
in principle with the Issuer Parties and the statutory committee of equity
security holders appointed on December 22, 2009 in the bankruptcy cases of the
Issuer Parties (the "Equity Committee") as to certain modifications to the
Modified Plan (as modified, the "Fourth Modified Plan of Reorganization"). The
Consenting Noteholders plan to enter into a Restructuring Plan Support
Agreement, which will supersede the Plan Support Agreement, with the Issuer
Parties and the Equity Committee setting forth certain agreements among them to
implement the Fourth Modified Plan of Reorganization (the "Restructuring Plan
Support Agreement").

Pursuant to the Fourth Modified Plan of Reorganization, the Noteholders would
receive, in exchange for their Notes, their pro-rata share of (i) between
$90,000,000 and $110,000,000 principal amount of New Senior Secured Notes, (ii)
$10,000,000 in cash (the "Cash Payment"), (iii) all cash proceeds from an
$85,000,000 rights offering (the "Rights Offering"), (iv) payment in cash of all
accrued but unpaid interest due under the Notes through the date of
effectiveness of the Issuer Parties' bankruptcy cases, and (v) $5,000,000 of
common stock of the reorganized Issuer, issued at a price of $1.80 per share
(the "Supplemental Equity Exchange").

The Rights Offering will consist of the Issuer Parties offering to all holders
of Common Stock, on a pro-rata basis, the right to purchase common stock of the
reorganized Issuer at a price of $1.80 per share. Pursuant to the Restructuring
Plan Support Agreement and related documents, the Consenting Noteholders will
agree to backstop the Rights Offering in its entirety with their Notes.
Therefore, to the extent the Rights Offering is not fully subscribed for by the
holders of Common Stock, the Consenting Noteholders will exchange a principal
amount of their Notes equal to any such shortfall into common stock of the
reorganized Issuer at a price of $1.80 per share. Notwithstanding the foregoing,
in connection with their backstop commitment, the Consenting Noteholders will
exchange no less than $20,000,000 in principal amount of their Notes for common
stock of the reorganized Issuer at $1.80 per share even if their backstop
commitment requires an exchange of less than this amount. For example, if the
holders of Common Stock elect not to participate in the Rights Offering, then
the Noteholders pursuant to their backstop commitment will exchange $85,000,000
in principal amount of Notes for common stock of the reorganized Issuer at a
price of $1.80 per share. When combined with the application of the Cash Payment
and Supplemental Equity Exchange, this will result in the issuance of an
aggregate principal amount of New Senior Secured Notes equal to $110,000,000.
However, if the Rights Offering is fully subscribed for by the holders of Common
Stock, the Noteholders will receive the cash proceeds of the Rights Offering in
satisfaction of $85,000,000 principal amount of Notes and the Consenting
Noteholders will exchange $20,000,000 in principal amount of Notes for common
stock of the reorganized Issuer at a price of $1.80 per share. When combined
with the application of the Cash Payment and Supplemental Equity Exchange, this
will result in the issuance of an aggregate







----------------------------                        -------------------------
CUSIP No.  36229U102            SCHEDULE 13D/A        Page 7 of 8 Pages

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principal amount of New Senior Secured Notes equal to $90,000,000.

The Consenting Noteholders will receive a fee of 5% of the backstop commitment
amount in exchange for their commitment to backstop the Rights Offering.

The Noteholders are entitled to receive a fee equal to 2% of the aggregate
principal amount of Notes currently outstanding in the event that at any time
prior to consummation of the Rights Offering a restructuring transaction other
than the restructuring transaction set forth in the Fourth Modified Plan of
Reorganization is consummated.

Pursuant to the Fourth Modified Plan of Reorganization, the initial board of
directors of the reorganized Issuer will consist of: two directors to be
selected by the Required Noteholders, two directors with expertise in the
Issuer's industry to be selected by the Equity Committee, one director to be
selected by mutual agreement of the Required Noteholders and the Equity
Committee, one director to be selected by the current Board of Directors from
the current Board of Directors of the Issuer, and the Chief Executive Officer of
the reorganized Issuer. The three holders of the largest principal amounts of
the Notes shall have board observer rights subject to reasonable restrictions.

This description of the agreement in principle reached by the Consenting
Noteholders, the Issuer Parties and the Equity Committee is a summary only and
is qualified in its entirety by reference to the Term Sheet for the Plan of
Reorganization of GSI Group, Inc. et al (the "Term Sheet"), a copy of which is
referenced as Exhibit 4 hereto (which incorporates by reference Exhibit 99.1 of
the Current Report on Form 8-K filed by the Issuer on May 11, 2010) and is
incorporated herein by reference.


ITEM 6.       CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH
RESPECT TO SECURITIES OF THE ISSUER

Item 6 of the Schedule 13D is hereby amended and supplemented by the addition of
the following:

     As described in Item 4 above, on May 7, 2010, the Consenting Noteholders
reached an agreement in principle with the Issuer Parties and the Equity
Committee as to the Fourth Modified Plan of Reorganization, the terms of which
are set forth in the Term Sheet a copy of which is referenced as Exhibit 4
hereto (which incorporates by reference Exhibit 99.1 of the Current Report on
Form 8-K filed by the Issuer on May 11, 2010) and is incorporated herein by
reference.


ITEM 7.       MATERIAL TO BE FILED AS EXHIBITS

Item 7 of the Schedule 13D is hereby amended and supplemented by the addition of
the following:

4. Term Sheet for the Plan of Reorganization of GSI Group, Inc. et al, dated as
of May 7, 2010 (incorporated by reference to Exhibit 99.1 of the Current Report
on Form 8-K filed by the Issuer on May 11, 2010).






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CUSIP No.  36229U102            SCHEDULE 13D        Page 8 of 8 Pages
----------------------------                        -------------------------

                                    Signature

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

     Dated: May 11, 2010

                                    /S/ Eric M. Ruttenberg
                                    ----------------------
                                    TINICUM LANTERN II L.L.C.,
                                    On its own behalf and
                                    as the General Partner of
                                    TINICUM CAPITAL PARTNERS II, L.P.
                                    By Eric M. Ruttenberg,
                                    Managing Member

                                    /s/ Terence M. O'Toole
                                    ----------------------
                                    Terence M. O'Toole

                                    /s/ Eric M. Ruttenberg
                                    ----------------------
                                    Eric M. Ruttenberg