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                                                                    EXHIBIT 4.12

                          FIRST SUPPLEMENTAL INDENTURE

               THIS FIRST SUPPLEMENTAL INDENTURE (this " First Supplemental
Indenture"), dated as of June 4, 2001, among Dresser Entech, Inc., and Ring-O
Valve, Incorporated (each, a "Guaranteeing Subsidiary" and collectively, the
"Guaranteeing Subsidiaries"), subsidiaries of Dresser, Inc. (or its permitted
successor), a Delaware corporation (the "Company"), the Company, the other
Guarantors (as defined in the Indenture referred to herein) and State Street
Bank and Trust Company, as trustee under the indenture referred to below (the
"Trustee").

                                   WITNESSETH:

               WHEREAS, the Company has heretofore executed and delivered to the
Trustee an indenture (the "Indenture"), dated as of April 10, 2001 providing for
the issuance of an aggregate principal amount of up to $300,000,000 million of 9
3/8% Senior Subordinated Notes due 2011 (the "Notes");

               WHEREAS, the Indenture provides that under certain circumstances
each Guaranteeing Subsidiary shall execute and deliver to the Trustee a
supplemental indenture pursuant to which each 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 First Supplemental Indenture.

               NOW THEREFORE, in consideration of the foregoing and for other
good and valuable consideration, the receipt of which is hereby acknowledged,
each 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. Each 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 each Guaranteeing
Subsidiary under its Guarantee pursuant to this First 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. Each 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 First 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 FIRST 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 First Supplemental Indenture. Each signed copy shall be an original, but
all of them together represent the same agreement.

               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 First
Supplemental Indenture or for or in respect of the recitals contained herein,
all of which recitals are made solely by each Guaranteeing Subsidiary and the
Company. IN WITNESS WHEREOF, the parties hereto have caused this First
Supplemental Indenture to be duly executed and attested, all as of the date
first above written.

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Dated:  June 4, 2001


                                        DRESSER ENTECH, INC.


                                        By: /s/ Frank P. Pittman
                                           -------------------------------------
                                        Name:   Frank P. Pittman
                                        Title:  Vice President and Asst.
                                        Secretary

                                        RING-O VALVE,  INCORPORATED


                                        By: /s/ Frank P. Pittman
                                           -------------------------------------
                                        Name:   Frank P. Pittman
                                        Title:  Vice President and Asst.
                                        Secretary


                                        STATE STREET BANK AND TRUST COMPANY,
                                        as Trustee


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