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                                                                     Exhibit 4.9


                         THIRD SUPPLEMENTAL INDENTURE



            THIRD SUPPLEMENTAL INDENTURE (this "Supplemental Indenture"), dated
as of April 24, 2002, among Modern Acquisition, Inc., a Delaware corporation,
(the "Guaranteeing Subsidiary"), and State Street Bank and Trust Company, as
trustee under the indenture referred to below (the "Trustee").

                              W I T N E S S E T H :

            WHEREAS, Dresser, Inc., a Delaware Corporation (the "Company"), and
the existing Guarantors (as defined in the Indenture referred to herein) have
heretofore executed and delivered to the Trustee an indenture (the "Indenture"),
dated as of April 10, 2001, and as amended on June 4, 2001 and June 12, 2001,
providing for the issuance of an aggregate principal amount of up to
$300,000,000 of 9 3/8% Senior Subordinated Notes due 2011 (the "Notes");

            WHEREAS, the Indenture provides that under certain circumstances the
Guaranteeing Subsidiary shall execute and deliver to the Trustee a supplemental
indenture pursuant to which the Guaranteeing Subsidiary shall unconditionally
guarantee all of the Company's Obligations under the Notes and the Indenture on
the terms and conditions set forth herein (the "Guarantee"); and

            WHEREAS, pursuant to Section 9.01 of the Indenture, the Trustee is
authorized to execute and deliver this Supplemental Indenture.

            NOW THEREFORE, in consideration of the foregoing and for other good
and valuable consideration, the receipt of which is hereby acknowledged, the
Guaranteeing Subsidiary and the Trustee mutually covenant and agree for the
equal and ratable benefit of the Holders of the Notes as follows:

            1.    CAPITALIZED TERMS. Capitalized terms used herein without
definition shall have the meanings assigned to them in the Indenture.

            2.    AGREEMENT TO GUARANTEE. The Guaranteeing Subsidiary hereby
agrees as follows:

                  (a)   Along with all Guarantors named in the Indenture, to
                        jointly and severally Guarantee to each Holder of a Note
                        authenticated and delivered by the Trustee and to the
                        Trustee and its successors and assigns, irrespective of
                        the validity and enforceability of the Indenture, the
                        Notes or the obligations of the Company hereunder or
                        thereunder, that:
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                        (i)   the principal of and interest on the Notes will be
                  promptly paid in full when due, whether at maturity, by
                  acceleration, redemption or otherwise, and interest on the
                  overdue principal of and interest on the Notes, if any, if
                  lawful, and all other obligations of the Company to the
                  Holders or the Trustee hereunder or thereunder will be
                  promptly paid in full or performed, all in accordance with the
                  terms hereof and thereof; and

                        (ii)  in case of any extension of time of payment or
                  renewal of any Notes or any of such other obligations, that
                  same will be promptly paid in full when due or performed in
                  accordance with the terms of the extension or renewal, whether
                  at stated maturity, by acceleration or otherwise. Failing
                  payment when due of any amount so guaranteed or any
                  performance so guaranteed for whatever reason, the Guarantors
                  shall be jointly and severally obligated to pay the same
                  immediately.

                  (b)   The obligations hereunder shall be unconditional,
                        irrespective of the validity, regularity or
                        enforceability of the Notes or the Indenture, the
                        absence of any action to enforce the same, any waiver or
                        consent by any Holder of the Notes with respect to any
                        provisions hereof or thereof, the recovery of any
                        judgment against the Company, any action to enforce the
                        same or any other circumstance which might otherwise
                        constitute a legal or equitable discharge or defense of
                        a guarantor.

                  (c)   The following is hereby waived: diligence, presentment,
                        demand of payment, filing of claims with a court in the
                        event of insolvency or bankruptcy of the Company, any
                        right to require a proceeding first against the Company,
                        protest, notice and all demands whatsoever.

                  (d)   This Guarantee shall not be discharged except by
                        complete performance of the obligations contained in the
                        Notes and the Indenture or pursuant to Section 6 hereof.

                  (e)   If any Holder or the Trustee is required by any court or
                        otherwise to return to the Company, the Guarantors, or
                        any custodian, Trustee, liquidator or other similar
                        official acting in relation to either the Company or the
                        Guarantors, any amount paid by either to the Trustee or
                        such Holder, this Guarantee, to the extent theretofore
                        discharged, shall be reinstated in full force and
                        effect.

                  (f)   No Guaranteeing Subsidiary shall be entitled to any
                        right of subrogation in relation to the Holders in
                        respect of any obligations guaranteed hereby until
                        payment in full of all obligations guaranteed hereby.
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                  (g)   As between the Guarantors, on the one hand, and the
                        Holders and the Trustee, on the other hand, (x) the
                        maturity of the obligations guaranteed hereby may be
                        accelerated as provided in Article 6 of the Indenture
                        for the purposes of this Guarantee, notwithstanding any
                        stay, injunction or other prohibition preventing such
                        acceleration in respect of the obligations guaranteed
                        hereby, and (y) in the event of any declaration of
                        acceleration of such obligations as provided in Article
                        6 of the Indenture, such obligations (whether or not due
                        and payable) shall forthwith become due and payable by
                        the Guarantors for the purpose of this Guarantee.

                  (h)   The Guarantors shall have the right to seek contribution
                        from any non-paying Guarantor so long as the exercise of
                        such right does not impair the rights of the Holders
                        under the Guarantee.

                  (i)   Pursuant to Section 11.03 of the Indenture, after giving
                        effect to any maximum amount and any other contingent
                        and fixed liabilities that are relevant under any
                        applicable Bankruptcy or fraudulent conveyance laws
                        (including, without limitation, all Senior Debt of such
                        Guarantor), and after giving effect to any collections
                        from, rights to receive contribution from or payments
                        made by or on behalf of any other Guarantor in respect
                        of the obligations of such other Guarantor under Article
                        11 of the Indenture shall result in the obligations of
                        such Guarantor under its Guarantee not constituting a
                        fraudulent transfer or conveyance.

            3.    SUBORDINATION. The Obligations of the Guaranteeing Subsidiary
under its Guarantee pursuant to this Supplemental Indenture shall be junior and
subordinated to the Senior Debt of such Guaranteeing Subsidiary on the same
basis as the Notes are junior and subordinated to the Senior Debt of the
Company. For the purposes of the foregoing sentence, the Trustee and the Holders
shall have the right to receive and/or retain payments by such Guaranteeing
Subsidiary only at such time as they may receive and/or retain payments in
respect of the Notes pursuant to the Indenture, including Article 10 thereof.

            4.    EXECUTION AND DELIVERY. The Guaranteeing Subsidiary agrees
that the Guarantees shall remain in full force and effect notwithstanding any
failure to endorse on each Note a notation of such Guarantee.

            5.    Guaranteeing Subsidiary May Consolidate, Etc. on Certain
Terms.

                  (a)   No Guaranteeing Subsidiary may consolidate with or merge
                        with or into (whether or not such Guarantor is the
                        surviving Person) another corporation, Person or entity
                        whether or not affiliated with such Guarantor unless:
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                        (i)   subject to Section 11.05 of the Indenture, the
                  Person formed by or surviving any such consolidation or merger
                  (if other than a Guarantor or the Company) shall be a
                  corporation organized and validly existing under the laws of
                  the United States or any state thereof or the District of
                  Columbia, and unconditionally assumes all the obligations of
                  such Guarantor, pursuant to a supplemental indenture in form
                  and substance reasonably satisfactory to the Trustee, under
                  the Notes, the Indenture and the Guarantee on the terms set
                  forth herein or therein;

                        (ii)  immediately after giving effect to such
                  transaction, no Default or Event of Default exists; and

                        (iii) the Company would be permitted, immediately after
                  giving effect to such transaction, to incur at least $1.00 of
                  additional Indebtedness (other than Permitted Indebtedness)
                  pursuant to Section 4.09 of the Indenture.

                  (b)   In case of any such consolidation, merger, sale or
                        conveyance and upon the assumption by the successor
                        Person, by supplemental indenture, executed and
                        delivered to the Trustee and satisfactory in form to the
                        Trustee, of the Guarantee endorsed upon the Notes and
                        the due and punctual performance of all of the covenants
                        and conditions of the Indenture to be performed by the
                        Guarantor, such successor Person shall succeed to and be
                        substituted for the Guarantor with the same effect as if
                        it had been named herein as a Guarantor. Such successor
                        Person thereupon may cause to be signed any or all of
                        the Guarantees to be endorsed upon all of the Notes
                        issuable hereunder which theretofore shall not have been
                        signed by the Company and delivered to the Trustee. All
                        the Guarantees so issued shall in all respects have the
                        same legal rank and benefit under the Indenture as the
                        Guarantees theretofore and thereafter issued in
                        accordance with the terms of the Indenture as though all
                        of such Guarantees had been issued at the date of the
                        execution hereof.

                  (c)   Except as set forth in Articles 4 and 5 of the
                        Indenture, and notwithstanding clauses(a)(iii) above,
                        nothing contained in the Indenture or in any of the
                        Notes shall prevent any consolidation or merger of a
                        Guarantor with or into the Company or another Guarantor,
                        or shall prevent any sale or conveyance of the property
                        of a Guarantor as an entirety or substantially as an
                        entirety to the Company or another Guarantor.

            6.    RELEASES. In the event of a sale or other disposition of all
of the assets of any Guarantor, by way of merger, consolidation or otherwise, or
a sale or other disposition of all to the capital stock of any Guarantor, then
such Guarantor (in the event of a sale or other disposition, by way of merger,
consolidation or otherwise, of all of the capital stock of such
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Guarantor) or the corporation acquiring the property (in the event of a sale or
other disposition of all or substantially all of the assets of such Guarantor)
will be released and relieved of any obligations under its Guarantee; provided
that the Net Cash Proceeds of such sale or other disposition are applied in
accordance with the applicable provisions of the Indenture, including without
limitation Section 4.10 of the Indenture. Upon delivery by the Company to the
Trustee of an Officers' Certificate and an Opinion of Counsel to the effect that
such sale or other disposition was made by the Company in accordance with the
applicable provisions of the Indenture, including without limitation Section
4.10 of the Indenture, the Trustee shall execute any documents reasonably
required in order to evidence the release of any Guarantor from its obligations
under its Guarantee.

            Any Guarantor not released from its obligations under its Guarantee
shall remain liable for the full amount of principal of and interest on the
Notes and for the other obligations of any Guarantor under the Indenture as
provided in Article 11 of the Indenture.

            7.    NO RECOURSE AGAINST OTHERS. No past, present or future
director, officer, employee, incorporator, stockholder or agent of any
Guaranteeing Subsidiary, as such, shall have any liability for any obligations
of the Company or any Guaranteeing Subsidiary under the Notes, any Guarantees,
the Indenture or this Supplemental Indenture or for any claim based on, in
respect of, or by reason of, such obligations or their creation. Each Holder of
the Notes by accepting a Note waives and releases all such liability. The waiver
and release are part of the consideration for issuance of the Notes. Such waiver
may not be effective to waive liabilities under the federal securities laws and
it is the view of the Commission that such a waiver is against public policy.

            8.    NEW YORK LAW TO GOVERN. THE INTERNAL LAW OF THE STATE OF NEW
YORK SHALL GOVERN AND BE USED TO CONSTRUE THIS SUPPLEMENTAL INDENTURE WITHOUT
GIVING EFFECT TO APPLICABLE PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT
THE APPLICATION OF THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

            9.    COUNTERPARTS. The parties may sign any number of copies of
this Supplemental Indenture. Each signed copy shall be an original, but all of
them together represent the same instrument.

            10.   EFFECT OF HEADINGS. The Section headings herein are for
convenience only and shall not affect the construction hereof.

            11.   THE TRUSTEE. The Trustee shall not be responsible in any
manner whatsoever for or in respect of the validity or sufficiency of this
Supplemental Indenture or for or in respect of the recitals contained herein,
all of which recitals are made solely by the Guaranteeing Subsidiary and the
Company.

            IN WITNESS WHEREOF, the parties hereto have caused this Supplemental
Indenture to be duly executed and attested, all as of the date first above
written.
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Dated:  April 24, 2002



                                                MODERN ACQUISITION, INC.



                                                By: /s/ JAMES A. NATTIER
                                                    ----------------------------
                                                Name:  James A. Nattier
                                                Title: Vice President


                                                STATE STREET BANK AND TRUST
                                                COMPANY , as Trustee


                                                By: /s/ PHILIP G. KANE
                                                    ----------------------------
                                                Name:  Philip G. Kane, Jr.
                                                Title: Vice President