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

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

                                 Amendment No. 3

                                 GSI Group Inc.

                                (Name of Issuer)

                           Common Stock, no par value

                         (Title of Class of Securities)

                                    36229U102

                                 (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)

                                 March 16, 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. 3 (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 and  Amendment  No. 2 filed on March 16,
2010, the "Schedule  13D") with respect to the common  stock,  no par value (the
"Shares"), 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 March 16, 2010 TCP II and the other Consenting  Noteholders entered into
an Amended and Restated  Noteholder  Restructuring  Plan Support  Agreement (the
"Amended and Restated Plan Support Agreement") with the Issuer Parties, amending
and  restating the Plan Support  Agreement.  Under the Amended and Restated Plan
Support  Agreement the parties thereto agreed to  modifications to the Plan (the
"Modified Plan") and to support the Modified Plan. The Amended and Restated Plan
Support  Agreement  contains specific  agreements by the Consenting  Noteholders
with respect to voting  their claims in support of the Modified  Plan as well as
conditions to the termination of the Amended and Restated Plan Support Agreement
which  are  substantially  similar  to  those  contained  in  the  Plan  Support
Agreement.

     As more fully  described in the Modified Plan,  under the Modified Plan the
Notes will be exchanged  for,  among other things,  New Senior Secured Notes (as
defined  in the  Modified  Plan) and New  Preferred  Shares  (as  defined in the
Modified Plan) which New Preferred  Shares will be convertible into common stock
of the  reorganized  Issuer.  The holders of the New Preferred  Shares will vote
together  with the holders of common  stock of the  reorganized  Issuer on an as
converted  basis. The terms of the New Preferred Shares are set forth as Exhibit
C to the Modified Plan. This  description of the Modified Plan is a summary only
and is qualified  in its  entirety by reference to the Modified  Plan, a copy of
which was filed as Exhibit A of Exhibit  10.1 of the Current  Report on Form 8-K
filed by the Issuer on March 19, 2010.

     This  description  of the Amended and Restated Plan Support  Agreement is a
summary  only and is  qualified  in its entirety by reference to the Amended and
Restated  Plan Support  Agreement,  a copy of which is  referenced  as Exhibit 3
hereto (which  incorporates  by reference  Exhibit 10.1 of the Current Report on
Form 8-K filed by the Issuer on March 19,  2010) and is  incorporated  herein by
reference.







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

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 March 16, 2010, the Consenting Noteholders
entered into the Amended and Restated  Plan  Support  Agreement  with the Issuer
Parties,  under which the parties thereto agreed to the terms of a restructuring
of the Notes  pursuant to the Modified  Plan, a copy of which is  referenced  as
Exhibit 3 hereto (which  incorporates  by reference  Exhibit 10.1 of the Current
Report on Form 8-K filed by the  Issuer on March 19,  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:

     3. Amended and Restated  Noteholder  Restructuring  Plan Support Agreement,
dated as of March 16,  2010,  by and among the  Consenting  Noteholders  and the
Issuer Parties  (incorporated by reference to Exhibit 10.1 of the Current Report
on Form 8-K filed by the Issuer on March 19, 2010).





----------------------------                        -------------------------
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: March 19, 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