Sec Form 3 Filing - SIGULER GUFF ADVISERS, LLC @ Fathom Digital Manufacturing Corp - 2021-12-23

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person SIGULER GUFF ADVISERS, LLC 2. Issuer Name and Ticker or Trading Symbol Fathom Digital Manufacturing Corp [ FATH] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 200 PARK AVE., 23RD FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 12/23/2021 (Street) NEW YORK, NY10166 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Class A Common Stock( 1 ) 8,597,214 I SIGULER GUFF SMALL BUYOUT OPPORTUNITIES FUND III, LP( 2 )( 3 ) Class A Common Stock( 1 ) 1,556,527 I SIGULER GUFF SMALL BUYOUT OPPORTUNITIES FUND III (F), LP( 2 )( 3 ) Class A Common Stock( 1 ) 234,974 I SIGULER GUFF SMALL BUYOUT OPPORTUNITIES FUND III (C), LP( 2 )( 3 ) Class A Common Stock( 1 ) 59,812 I SIGULER GUFF SMALL BUYOUT OPPORTUNITIES III (UK), LP( 2 )( 3 ) Class A Common Stock( 1 ) 2,416,676 I SIGULER GUFF HP OPPORTUNITIES FUND II, LP( 2 )( 3 ) Class A Common Stock( 1 ) 1,375,668 I SIGULER GUFF AMERICAS OPPORTUNITIES FUND, LP( 2 )( 3 ) Class B Common Stock 2,300,994 I SIGULER GUFF SMALL BUYOUT OPPORTUNITIES FUND III (T), LP( 2 )( 3 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Earnout Shares( 4 ) ( 4 ) ( 4 ) ( 4 ) Class A Common Stock 637,448 I SIGULER GUFF SMALL BUYOUT OPPORTUNITIES FUND III, LP Earnout Shares( 5 ) ( 5 ) ( 5 ) ( 5 ) Class A Common Stock 115,410 I SIGULER GUFF SMALL BUYOUT OPPORTUNITIES FUND III (F), LP Earnout Shares( 6 ) ( 6 ) ( 6 ) ( 6 ) Class A Common Stock 17,422 I SIGULER GUFF SMALL BUYOUT OPPORTUNITIES FUND III (C), LP Earnout Shares( 7 ) ( 7 ) ( 7 ) ( 7 ) Class A Common Stock 4,435 I SIGULER GUFF SMALL BUYOUT OPPORTUNITIES III (UK), LP Earnout Shares( 8 ) ( 8 ) ( 8 ) ( 8 ) Class A Common Stock 179,187 I SIGULER GUFF HP OPPORTUNITIES FUND II, LP Earnout Shares( 9 ) ( 9 ) ( 9 ) ( 9 ) Class A Common Stock 102,000 I SIGULER GUFF AMERICAS OPPORTUNITIES FUND, LP Earnout Shares( 10 ) ( 10 ) ( 10 ) ( 10 ) Class B Common Stock 170,431 I SIGULER GUFF SMALL BUYOUT OPPORTUNITIES FUND III (T), LP Earnout Shares( 10 ) ( 10 ) ( 10 ) ( 10 ) Class A LLC Units 170,431 I SIGULER GUFF SMALL BUYOUT OPPORTUNITIES FUND III (T), LP Class A LLC Units( 11 ) ( 11 ) ( 11 ) ( 11 ) Class A Common Stock 2,300,994 I SIGULER GUFF SMALL BUYOUT OPPORTUNITIES FUND III (T), LP

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other SIGULER GUFF ADVISERS, LLC 200 PARK AVE., 23RD FLOOR NEW YORK, NY10166 X Signatures SIGULER GUFF ADVISERS, LLC, BY: SIGULER GUFF & COMPANY, LP, BY: SIGULER GUFF HOLDINGS GP, LLC, /s/Joshua Posner, as Authorized Person 01/03/2022 Signature of Reporting Person Date

Explanation of Responses:

( 1 )On December 23, 2021 (the "Effective Time"), the Issuer, formerly known as Altimar Acquisition Corp. II, acquired Fathom Holdco, LLC ("Fathom") pursuant to a Business Combination Agreement by and among the Issuer, Fathom and certain other parties thereto (the "Business Combination Agreement"). Pursuant to the Business Combination Agreement, at the Effective Time, the outstanding equity interests of Fathom held by the Reporting Person were converted into the right to receive shares of the Issuer's Class A Common Stock or a combination of the Issuer's Class B Common Stock and a like number of Fathom's Class A LLC Units, as applicable. Shares of Class B Common Stock have no economic rights (other than the right to receive the par value of such shares in connection with the liquidation, dissolution or winding up of the Issuer), and each share of Class B Common Stock entitles its holder to one vote per share. ( 2 )This statement is filed by Siguler Guff Advisers, LLC ("SGA"). SGA is a registered investment adviser to Siguler Guff Small Buyout Opportunities Fund III, LP ("SBOF III"), Siguler Guff Small Buyout Opportunities Fund III (F), LP ("SBOF III (F)"), Siguler Guff Small Buyout Opportunities Fund III (C), LP ("SBOF III (C)"), Siguler Guff Small Buyout Opportunities III (UK), LP ("SBOF III (UK)"), Siguler Guff HP Opportunities Fund II, LP ("SG HP") and Siguler Guff Americas Opportunities Fund, LP ("SG Americas", and together with SBOF III, SBOF III (F), SBOF III (C), SBOF III (UK) and SG HP, the "SG Funds") that directly hold the securities of the Issuer to which this statement relates for the benefit of their respective investors, and in such capacity SGA has voting and dispositive power over such securities. SGA is 100% owned by Siguler Guff & Company, LP. ( 3 )(Continued from footnote 2) The general partner of Siguler Guff & Company, LP is Siguler Guff Holdings GP, LLC. Each of Siguler Guff SBOF III GP, LLC ("SBOF III GP"), Siguler Guff SBOF III (UK) GP, LLP ("SBOF III (UK) GP"), Siguler Guff HP II GP, LLC ("SG HP GP"), and Siguler Guff Americas GP, LLC ("SG Americas GP" and together with SBOF III GP, SBOF III (UK) GP and SG HP GP, the "SG Fund GPs"), which are the general partners of the applicable SG Funds, is controlled by its sole member, Siguler Guff Capital, LP, which is majority controlled by Andrew Guff and George Siguler. Consequently, Siguler Guff Capital, LP, Andrew Guff and George Siguler may be deemed the beneficial owners of the shares held by the Funds. George W. Siguler, Andrew J. Guff, Donald P. Spencer and Kenneth J. Burns are the owners of Siguler Guff Holdings GP, LLC and the executive officers of SGA. ( 4 )The Reporting Person holds an aggregate of 637,448 shares of Class A Common Stock that are subject to forfeiture. These earnout shares will vest in three equal tranches, with each tranche vesting at each of the following share price thresholds: $12.50, $15.00 and $20.00. The achievement of the price threshold will be determined based on a volume-weighted average price ("VWAP") of the Class A Common Stock for 20 trading days within any 30 trading day period or a change of control transaction of the issuer that implies the same per share value as the applicable price threshold. The earnout period will be five years from the date of the closing of the Business Combination or December 23, 2026. If such vesting requirements are not achieved during the five-year earnout period, such earnout shares will be forfeited. ( 5 )The Reporting Person holds an aggregate of 115,410 shares of Class A Common Stock that are subject to forfeiture. These earnout shares will vest in three equal tranches, with each tranche vesting at each of the following share price thresholds: $12.50, $15.00 and $20.00. The achievement of the price threshold will be determined based on a VWAP of the Class A Common Stock for 20 trading days within any 30 trading day period or a change of control transaction of the issuer that implies the same per share value as the applicable price threshold. The earnout period will be five years from the date of the closing of the Business Combination or December 23, 2026. If such vesting requirements are not achieved during the five-year earnout period, such earnout shares will be forfeited. ( 6 )The Reporting Person holds an aggregate of 17,422 shares of Class A Common Stock that are subject to forfeiture. These earnout shares will vest in three equal tranches, with each tranche vesting at each of the following share price thresholds: $12.50, $15.00 and $20.00. The achievement of the price threshold will be determined based on a VWAP of the Class A Common Stock for 20 trading days within any 30 trading day period or a change of control transaction of the issuer that implies the same per share value as the applicable price threshold. The earnout period will be five years from the date of the closing of the Business Combination or December 23, 2026. If such vesting requirements are not achieved during the five-year earnout period, such earnout shares will be forfeited. ( 7 )The Reporting Person holds an aggregate of 4,435 shares of Class A Common Stock that are subject to forfeiture. These earnout shares will vest in three equal tranches, with each tranche vesting at each of the following share price thresholds: $12.50, $15.00 and $20.00. The achievement of the price threshold will be determined based on a VWAP of the Class A Common Stock for 20 trading days within any 30 trading day period or a change of control transaction of the issuer that implies the same per share value as the applicable price threshold. The earnout period will be five years from the date of the closing of the Business Combination or December 23, 2026. If such vesting requirements are not achieved during the five-year earnout period, such earnout shares will be forfeited. ( 8 )The Reporting Person holds an aggregate of 179,187 shares of Class A Common Stock that are subject to forfeiture. These earnout shares will vest in three equal tranches, with each tranche vesting at each of the following share price thresholds: $12.50, $15.00 and $20.00. The achievement of the price threshold will be determined based on a VWAP of the Class A Common Stock for 20 trading days within any 30 trading day period or a change of control transaction of the issuer that implies the same per share value as the applicable price threshold. The earnout period will be five years from the date of the closing of the Business Combination or December 23, 2026. If such vesting requirements are not achieved during the five-year earnout period, such earnout shares will be forfeited. ( 9 )The Reporting Person holds an aggregate of 102,000 shares of Class A Class A Common Stock that are subject to forfeiture. These earnout shares will vest in three equal tranches, with each tranche vesting at each of the following share price thresholds: $12.50, $15.00 and $20.00. The achievement of the price threshold will be determined based on a VWAP of the Class A Common Stock for 20 trading days within any 30 trading day period or a change of control transaction of the issuer that implies the same per share value as the applicable price threshold. The earnout period will be five years from the date of the closing of the Business Combination or December 23, 2026. If such vesting requirements are not achieved during the five-year earnout period, such earnout shares will be forfeited. ( 10 )The Reporting Person holds an aggregate of 170,431 of the Issuer's Class A LLC Units (the "Earnout Units") and 170,431 shares of the Issuer's Class B Common Stock that are subject to forfeiture (the "Earnout Shares"). The Earnout Units and Earnout Shares will vest in three equal tranches, with each tranche vesting at each of the following share price thresholds: $12.50, $15.00 and $20.00. The achievement of the price threshold will be determined based on a VWAP of the Issuer's Class A Common Stock, for 20 trading days within any 30 trading day period or a change of control transaction of the issuer that implies the same per share value as the applicable price threshold. The earnout period will be five years from the date of the closing of the Business Combination or December 23, 2026. If such vesting requirements are not achieved during the five-year earnout period, such earnout shares will be forfeited. ( 11 )The Class A LLC Units are exchangeable (upon delivery of a corresponding number of shares of the Issuer's Class B Common Stock (as reported on Table I hereof)) for shares of the Issuer's Class A Common Stock on a one-for-one basis or an equivalent amount of cash at the option of Fathom pursuant to the terms of the Second Amended and Restated LLC Operating Agreement of Fathom.

Remarks: Exhibit 24 - Powers of Attorney

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