UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
SCHEDULE 13G
(AMENDMENT NO. 6)
MKS Instruments, Inc.
(Name of Issuer)
Common Stock
(Title of Class of Securities)
55306N 10 4
(CUSIP Number)
December 15, 2006
(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)
[ ] Rule 13d-1(c)
[X] Rule 13d-1(d)
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CUSIP No. 55306N 10 4 13G Page 2 of Page 6
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1 NAMES OF REPORTING PERSONS.
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
Claire R. Bertucci
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2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
(a) [ ]
(b) [ ]
Not Applicable
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3 SEC USE ONLY
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4 CITIZENSHIP OR PLACE OF ORGANIZATION
United States
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5 SOLE VOTING POWER
0
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NUMBER OF 6 SHARED VOTING POWER
SHARES
BENEFICIALLY 6,624,666 (1)
OWNED BY -----------------------------------------------------------------
EACH 7 SOLE DISPOSITIVE POWER
REPORTING
PERSON 6,624,666 (1)
WITH -----------------------------------------------------------------
8 SHARED DISPOSITIVE POWER
0
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9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
6,624,666(1)
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10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*
Not Applicable
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11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9
11.7%
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12 TYPE OF REPORTING PERSON*
IN
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* See Instructions before filling out
(1) Consists of shares beneficially owned as of December 15, 2006. Shares in
Rows 7, 8 and 9 also include 3,161,580 beneficially owned by John R.
Bertucci, Mrs. Bertucci's spouse, with respect to which Mrs. Bertucci
disclaims beneficial ownership.
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CUSIP No. 55306N 10 4 13G Page 3 of Page 6
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Item 1(a). Name of Issuer:
MKS Instruments, Inc.
Item 1(b). Address of Issuer's Principal Executive Offices:
90 Industrial Way
Wilmington, MA 01887
Item 2(a). Name of Person Filing:
Claire R. Bertucci
Item 2(b). Address of Principal Business Office or, if None, Residence:
The address of the reporting persons is:
c/o MKS Instruments, Inc.
90 Industrial Way
Wilmington, MA 01887
Item 2(c). Citizenship:
Mrs. Bertucci is a citizen of the United States.
Item 2(d). Title of Class of Securities:
Common Stock, no par value per share.
Item 2(e). CUSIP Number:
CUSIP No. 55306N 10 4
Item 3. If This Statement is Filed Pursuant to Section 240.13d-1(b), or
240.13d-2(b) or (c), Check Whether the Person Filing is a:
Not Applicable.
(a) [ ] Broker or dealer registered under Section 15 of the Act
(15 U.S.C. 78o).
(b) [ ] Bank as defined in Section 3(a)(6) of the Exchange Act (15
U.S.C. 78c).
(c) [ ] Insurance company as defined in Section 3(a)(19) of the
Exchange Act (15 U.S.C. 78c).
(d) [ ] Investment company registered under Section 8 of the
Investment Company Act of 1940 (15 U.S.C. 80a-8).
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CUSIP No. 55306N 10 4 13G Page 4 of Page 6
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(e) [ ] An investment adviser in accordance with
Section 240.13d-1(b)(1)(ii)(E);
(f) [ ] An employee benefit plan or endowment fund in accordance
with Section 240.13d-1(b)(1)(ii)(F);
(g) [ ] A parent holding company or control person in accordance
with Section 240.13d-1(b)(1)(ii)(G);
(h) [ ] A savings association as defined in Section 3(b) of the
Federal Deposit Insurance Act (12 U.S.C. 1813);
(i) [ ] A church plan that is excluded from the definition of an
investment company under Section 3(c)(14) of the Investment
Company Act of 1940 (15 U.S.C. 80a-3);
(j) [ ] Group, in accordance with Section 240.13d-1(b)(1)(ii)(J).
Item 4. Ownership:
The filing of this statement shall not be construed as an admission
that any of the reporting persons are, for the purpose of Section 13(d) or 13(g)
of the Act, the beneficial owners of any securities covered under this
Statement.
(a) Amount Beneficially Owned by Claire R. Bertucci: 6,624,666 shares
(2)
(b) Percent of Class: 11.7%
(c) Number of Shares as to which Claire R. Bertucci has:
(i) Sole power to vote or to direct the vote: 0 shares
(ii) Shared power to vote or to direct the vote: 6,624,666 shares
(2)
(iii) Sole power to dispose or to direct the disposition of:
6,624,666 (2) shares
(iv) Shared power to dispose or to direct the disposition of: 0
shares
(2) Consists of shares beneficially owned as of December 15, 2006. Shares
reported in Row 4(a) also include 3,161,580 shares beneficially owned by
John R. Bertucci, Mrs. Bertucci's spouse, with respect to which Mrs.
Bertucci disclaims beneficial ownership.
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CUSIP No. 55306N 10 4 13G Page 5 of Page 6
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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 person has ceased to be the beneficial
owner of more than 5% 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.
Not applicable
Item 8. Identification and Classification of Members of the Group.
Not applicable
Item 9. Notice of Dissolution of Group.
Not applicable
Item 10. Certification.
Not applicable
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CUSIP No. 55306N 10 4 13G Page 6 of Page 6
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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: December 22, 2006
/s/ Claire R. Bertucci
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Claire R. Bertucci