[Form 4] OLD SECOND BANCORP INC Insider Trading Activity

Rhea-AI Filing Summary

Richard A. Gartelmann Jr., EVP and director of Old Second Bancorp, Inc. (OSBC), reported transactions dated 09/30/2025. The filing shows 44 shares of Old Second common stock were allocated to a 401(k) plan account during the third quarter at a $0 price and are recorded as held indirectly in a plan account, increasing the reported indirect holding to 12,516 shares. The form also records dispositions of 26,874 shares held in the reporting person’s name and 20,552 restricted stock units disposed, with an explanatory note that the 44 newly allocated shares were provided by the Plan Trustee as of 09/30/2025. The filing is signed by an attorney-in-fact on 10/01/2025.

Insights

Securities Analyst

TL;DR: Insider recorded a small 401(k) allocation and reported large dispositions of both common shares and restricted stock units on 09/30/2025.

The filing documents routine plan allocations alongside substantial disposals: a 44-share allocation to a 401(k) plan increased indirect holdings to 12,516 shares, while 26,874 shares registered in the reporting person’s name and 20,552 restricted stock units were reported as disposed. For investors, the allocation is immaterial but the reported disposals are sizeable in absolute terms; the form does not state prices or reasons for the dispositions, nor whether proceeds were tax- or diversification-driven.

Corporate Governance Expert

TL;DR: Filing reflects standard Section 16 reporting: plan allocation and notable share/unit disposals, signed by attorney-in-fact.

The disclosure appears procedurally complete: name, relationship (EVP and director), transaction dates, and explanatory notes are provided. The 401(k) allocation is explicitly noted as coming from the Plan Trustee. Signature by an attorney-in-fact is included with date 10/01/2025. The form does not include transaction prices for the dispositions or statement of purpose, so no further governance conclusions can be drawn from this filing alone.

SEC Form 4

FORM 4

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
or Section 30(h) of the Investment Company Act of 1940

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

1. Name and Address of Reporting Person^*

Gartelmann Richard A JR

(Last) (First) (Middle)

37 S. RIVER ST.

(Street)

AURORA IL 60506

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
OLD SECOND BANCORP INC [ OSBC ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	EVP

3. Date of Earliest Transaction (Month/Day/Year)
09/30/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	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
Old Second Bancorp, Inc. Common Stock	09/30/2025		J	V	44	A	$0	12,516(1)	I	By 401-K
Old Second Bancorp, Inc. Common Stock								26,874(2)	D
Restricted Stock Units								20,552	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 (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	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 (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (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: 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

Explanation of Responses:

1. Of this total, 44 shares were allocated during the third quarter pursuant to the Old Second Bancorp, Inc. Salary and Savings Plan. Information was provided herein by the Plan Trustee as of 9-30-25.

2. These shares are held in the reporting person's name alone.

	/s/ Shirley Cantrell, Attorney-in-Fact	10/01/2025
	** Signature of Reporting Person	Date
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).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
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