# EDGAR Filing Document

**Accession Number:** 0000357173
**File Stem:** 0001415889-25-019465
**Filing Date:** 2025-7
**Character Count:** 4644
**Document Hash:** dbb676861f1794d6fcbd58c970689b3d
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001415889-25-019465.hdr.sgml**: 20250708

**ACCESSION NUMBER**: 0001415889-25-019465

**CONFORMED SUBMISSION TYPE**: 3

**PUBLIC DOCUMENT COUNT**: 1

**CONFORMED PERIOD OF REPORT**: 20250701

**FILED AS OF DATE**: 20250708

**DATE AS OF CHANGE**: 20250708

**REPORTING-OWNER**: 

**OWNER DATA:**
- **COMPANY CONFORMED NAME:** Campbell Darin Patrick
- **CENTRAL INDEX KEY:** 0002074132

**ORGANIZATION NAME:**

**FILING VALUES:**
- **FORM TYPE:** 3
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 000-10537
- **FILM NUMBER:** 251110421

**MAIL ADDRESS:**
- **STREET 1:** 37 SOUTH RIVER ST.
- **CITY:** AURORA
- **STATE:** IL
- **ZIP:** 60507
**ISSUER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** OLD SECOND BANCORP INC
- **CENTRAL INDEX KEY:** 0000357173
- **STANDARD INDUSTRIAL CLASSIFICATION:** STATE COMMERCIAL BANKS [6022]
- **ORGANIZATION NAME:** 02 Finance
- **EIN:** 363143493
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**BUSINESS ADDRESS:**
- **STREET 1:** 37 S RIVER ST
- **CITY:** AURORA
- **STATE:** IL
- **ZIP:** 60507
- **BUSINESS PHONE:** 6308920202

**MAIL ADDRESS:**
- **STREET 1:** 37 SOUTH RIVER STREET
- **CITY:** AURORA
- **STATE:** IL
- **ZIP:** 60507

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## FORM 3

### INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

[ ] 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**<sup>*</sup><br>Campbell Darin Patrick<br><sub>(Last) (First) (Middle)</sub><br>37 S. RIVER ST.<br><sub>(Street)</sub><br>AURORA, IL 60506<br><sub>(City) (State) (Zip)</sub> | **3. Issuer Name and Ticker or Trading Symbol**<br>OLD SECOND BANCORP INC [ OSBC ] | **5. If Amendment, Date of Original Filed (Month/Day/Year)**<br>  |
| **2. Date of Event Requiring Statement (Month/Day/Year)**<br>2025-07-01 | **4. Relationship of Reporting Person(s) to Issuer**<br>(Check all applicable)<br>[X] Director   [ ] 10% Owner<br>[X] Officer (give title below)   [ ] Other (specify below)<br>_President, Powersports Lending_ | **6. Individual or Joint/Group Filing (Check Applicable Line)**<br>[X] Form filed by One Reporting Person<br>[ ] Form filed by More than One Reporting Person |

---

## Table I - Non-Derivative Securities Beneficially Owned

---

|  |  |  |  |
| --- | --- | --- | --- |
| 1. Title of Security | 2. Amount of Securities Beneficially Owned | 3. Ownership Form | 4. Nature of Indirect Beneficial Ownership |
| Old Second Bancorp, Inc. Common Stock | 309680<sup>(1)</sup> | D |  |

---

## Table II - Derivative Securities Beneficially Owned

---

|  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
| 1. Title of Derivative Security | 2. Date Exercisable and Expiration Date (Month/Day/Year) | 2. Date Exercisable and Expiration Date (Month/Day/Year) | 3. Title and Amount of Underlying Securities | 3. Title and Amount of Underlying Securities | 4. Conversion or Exercise Price | 5. Ownership Form | 6. Nature of Indirect Beneficial Ownership |
| 1. Title of Derivative Security | Date Exercisable | Expiration Date | Title | Amount or Number of Shares | 4. Conversion or Exercise Price | 5. Ownership Form | 6. Nature of Indirect Beneficial Ownership |
|  |  |  |  |  |  |  |  |

---

### Footnotes:

(1) These securities are issuable pursuant to the merger of Bancorp Financial, Inc. with and into Old Second Bancorp, Inc., which became effective on July 1, 2025. The reporting person held 119,966 shares of Bancorp Financial, Inc., which pursuant to the merger agreement, will be converted into 309,680 shares of Old Second Bancorp, Inc. common stock. The exchange of shares has not yet occurred, but the right to receive the shares is fixed and irrevocable under the merger agreement.

**Signature:** /s/ Shirley Cantrell, Attorney-in-Fact  
**Date:** 2025-07-08

### Remarks:

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.

**Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.**