Sec Form 4 Filing - HIGHBRIDGE CAPITAL MANAGEMENT LLC @ A. M. Castle & Co. - 2020-03-27

FORM 4 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 HIGHBRIDGE CAPITAL MANAGEMENT LLC 2. Issuer Name and Ticker or Trading Symbol A. M. Castle & Co. [ CTAM] 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) 277 PARK AVE, 23RD FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 03/27/2020 (Street) NEW YORK, NY10172 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 Common Stock, par value $0.01 per share ("Common Stock") 03/27/2020 J 22,519,492 A 23,028,594 I See footnote ( 4 )

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 5.0% / 7.0% Convertible Sr Secured PIK Toggle Notes due 2022 ( 2 ) 03/27/2020 J ( 2 ) ( 2 ) Common Stock, par value $0.01 per share ( 1 ) ( 1 ) ( 1 ) $ 0 I See footnote ( 4 ) 3.0% / 5.0% Convertible Sr Secured PIK Toggle Notes due 2024 ( 2 ) 03/27/2020 J ( 2 ) ( 2 ) Common Stock, par value $0.01 per share ( 3 ) 66,899,079 ( 1 ) $ 30,492,345 I See footnote ( 4 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other HIGHBRIDGE CAPITAL MANAGEMENT LLC 277 PARK AVE 23RD FLOOR NEW YORK, NY10172 X Signatures Highbridge Capital Management, LLC, By: /s/ John Oliva, its Managing Director 03/31/2020 Signature of Reporting Person Date

Explanation of Responses:

( 1 )On March 27, 2020, the Issuer completed an exchange transaction (the "Exchange"), whereby it issued new 3.00%/5.00% Convertible Senior PIK Toggle Notes due 2024 (the "New Notes") and shares of its Common Stock in exchange for its existing 5.00%/7.00% Convertible Senior PIK Toggle Notes due 2022 (the "Old Notes"). In connection with the Exchange, the Reporting Persons received an aggregate of 22,519,492 shares of Common Stock and $30,492,345 in aggregate principal amount of New Notes in exchange for $60,962,432.00 in aggregate principal amount of Old Notes beneficially owned by the Reporting Persons, plus accrued and unpaid interest thereon. ( 2 )The New Notes are convertible at the election of the holder at any time prior to the close of business on the trading day immediately preceding August 31, 2024, the maturity date of the New Notes. The New Notes are convertible into shares of Common Stock at an initial conversion rate of 2.1939631 shares of Common Stock per $1.00 principal amount of New Notes (subject to adjustment in certain circumstances). ( 3 )Upon conversion of the New Notes, the settlement of the conversion right may, at the option of the Issuer, be in the form of shares of Common Stock, cash or a combination of cash and shares of Common Stock. ( 4 )The securities reported herein are held by (i) Highbridge MSF International Ltd., a Cayman Islands exempted company ("MSF International") and (ii) Highbridge Tactical Credit Master Fund, L.P., a Cayman Islands exempted limited partnership ("Highbridge Tactical" and together with MSF International, the "Funds"). Highbridge Capital Management, LLC serves as the trading manager of the Funds. Each Reporting Person disclaims beneficial ownership of the securities reported herein except to the extent of such Reporting Person's pecuniary interest therein.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

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