UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 Mesa Royalty Trust (Name of Issuer) Units of Beneficial Interest (Title of Class of Securities) 590660106 (CUSIP Number) Check the following box if a fee is being paid with this statement / /. (A fee is not required only if the filing person: (1) has a previous statemen on file reporting beneficial ownership of more than five percent of the class of securities described in Item 1; and (2) has filed no amendment subsequent thereto reporting beneficial ownership of five percent or less of such class.) (See Rule 13d-7). *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 the disclosures provided in prior cover page. The information required in 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). SEC 1745 (10-88) Page 1 of 5 SCHEDULE 13G CUSIP NO. 590660106 1. NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON Beck, Mack & Oliver LLC 13-0477010 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) / /. (b) / /. 3. SEC USE ONLY 4. CITIZENSHIP OR PLACE OF ORGANIZATION New York 5. SOLE VOTING POWER 0 NUMBER OF SHARES 6. SHARED VOTING POWER BENEFICIALLY 0 OWNED BY EACH 7. SOLE DISPOSITIVE POWER REPORTING 0 PERSON WITH 8. SHARED DISPOSITIVE POWER 296,868 shares 9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 296,868 shares 10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* / /. 11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 15.93% 12. TYPE OF REPORTING PERSON* IA *SEE INSTRUCTION BEFORE FILLING OUT! Page 2 of 5 STATEMENT ON SCHEDULE 13G Item 1(a). Name of Issuer: Mesa Royalty Trust Item 1(b). Address of Issuer's Principal Executive Offices: 712 Main Street Houston, Texas 77002 Item 2(a). Names of Person Filing: Beck, Mack & Oliver LLC Item 2(b). Address of Principal Business Office or, if none, Residence: 330 Madison Avenue New York, New York 10017 Item 2(c). Citizenship: New York Item 2(d). Title of Class of Securities: Units of Beneficial Interest Item 2(e). CUSIP Number: 590660106 Item 3. If this statement is filed pursuant to Rules 13d-1(b), or 13d-2(b), check whether the person filing is a: (a) / / Broker or Dealer registered under Section 15 of the Act (b) / / Bank as defined in section 3(a)(6) of the Act (c) / / Insurance Company as defined in section 3(a)(19) of the Act (d) / / Investment Company registered under section 8 of the Investment Company Act (e) /X/ Investment Advisor registered under section 203 of the Investment Advisers Act (f) / / Employee Benefit Plan, Pension Fund which is subject to the provisions of the Employee Retirement Income Security Act of 1974 or Endowment Fund; see Section 240.13d-1(b)(ii)(F) (Note: See Item 7) Page 3 of 5 (g) / / Parent Holding Company, in accordance with Section 240.13d-1(b)(ii) (G). (Note: See Item 7) (h) / / Group, in accordance with Sec. 240.13d-1(b)(ii)(H). Item 4. Ownership: (a) Amount Beneficially Owned: 296,868 of 31st December, 2000 (b) Percent of Class: 15.93% (c) Number of shares as to which such person has: (i) sole power to vote or to direct the vote: (ii) shared power to vote or to direct the vote: (iii) sole power to dispose or to direct the disposition of: (iv) shared power to dispose or to direct the disposition of: 296,868 Item 5. Ownership of Five Percent or Less of a Class: Not Applicable Item 6. Ownership of More than Five Percent on Behalf of Another Person: See Item 6 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: By signing below, I certify that, to the best of my knowledge and belief, the securities referred to above were acquired in the ordinary course of business and were not acquired for the purpose of and do not have the effect of changing or influencing the control of the issuer of such securities and were not acquired in connection with or as a participant in any transaction having such purposes or effect. Page 4 of 5 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: 17th January, 2001 /s/ Robert C. Beck ------------------------ Name: Robert C. Beck Title: Senior Member ITEM 6 OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON The securities covered by this statement are owned by investment advisory clients of BECK, MACK & OLIVER LLC. These clients have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities. No one of these clients owns more than 5% of such class of securities. Page 5 of 5