Sec Form 4 Filing - Zimmerly Ronald Len Jr. @ MIDDLEFIELD BANC CORP - 2023-12-01

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 Zimmerly Ronald Len Jr. 2. Issuer Name and Ticker or Trading Symbol MIDDLEFIELD BANC CORP [ MBCN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 15985 EAST HIGH STREET 3. Date of Earliest Transaction (MM/DD/YY) 12/01/2023 (Street) MIDDLEFIELD, OH44062 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 12/01/2023 A( 1 ) 3,788 A $ 29.34 35,988 D Common Stock 12/01/2023 F 1,112 D $ 29.34 34,876 D

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 Conditional Stock Award ( 2 ) $ 27.4 ( 2 ) 03/10/2026 Common Stock 3,722 3,722 D Conditional Stock Award ( 3 ) $ 28.6 ( 3 ) 12/01/2025 Common Stock 7,576 7,576 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Zimmerly Ronald Len Jr. 15985 EAST HIGH STREET MIDDLEFIELD, OH44062 X Signatures /s/ Ronald L. Zimmerly, Jr. by Julie E. Shaw Power of Attorney 01/08/2024 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The acquisition represents the vesting of restricted stock granted to the reporting person on December 1, 2022. The shares vested on the first anniversary of the grant date. ( 2 )Until the award vests, the award confers no right to vote, no right to dividends, and no other shareholder rights to the recipient. Vesting is subject to a time-based or service condition and a performance-based condition. The details of the vesting conditions may be found in a Form 8kK filing dated March 17, 2023. ( 3 )The award represents a grant of restricted stock which vests ratably over a three-year period provided that Mr. Zimmerly remains continuously employed by Middlefield as of each vesting date. Until the award vests, the award confers no right to vote, no right to dividends, and no other shareholder rights to the recipent.

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

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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