Company: OSBC
Filing Date: 2025-05-08
Form Type: 424B3
Source: 0001104659-25-046065
Chunk: 46

Company: OLD SECOND BANCORP INC
Filing Date: 2025-05-08
Form: 424B3
Chunk 46
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 meeting will be held virtually on June 18, 2025, at 9:00 A.M. Central Time.

The Bancorp Financial special meeting will be held virtually only, via the internet — there will be no physical location for the special meeting .

Bancorp Financial stockholders can attend the Bancorp Financial special meeting by visiting the website https://web.lumiconnect.com/239103630 (passcode: bancorp2025) prior to the start of the meeting. Please note that this website address is case sensitive. Once you have logged in, you may listen to the meeting on a computer or through a telephone number that will be provided. However, please note that if you wish to ask a question during the special meeting, you will only be able to do so through your computer and you will not be able to ask a question over the telephone.

### Purpose of Bancorp Financial Special Meeting
At the Bancorp Financial special meeting, Bancorp Financial stockholders will be asked to vote on the following:

•

the merger proposal;

•

the stockholders agreement amendment proposal; and

•

the adjournment proposal.

Completion of the merger is conditioned on the approval of the merger proposal and the stockholders agreement amendment proposal. Completion of the merger is not conditioned on approval of the adjournment proposal.

### Recommendation of the Bancorp Financial Board of Directors
The Bancorp Financial board of directors recommends that Bancorp Financial stockholders vote “

#### FOR
” the merger proposal, “

#### FOR
” the stockholders agreement amendment proposal, and “

#### FOR
” the adjournment proposal. See “The Merger — Recommendation of the Bancorp Financial Board of Directors and Reasons for the Merger” beginning on page 39.

### Bancorp Financial Record Date; Stockholders Entitled to Vote
The Bancorp Financial board of directors has fixed the close of business on May 6, 2025 as the record date for determining the holders of Bancorp Financial common stock entitled to receive notice of, and to vote at, the Bancorp Financial special meeting. As of the record date, there were 2,813,992 shares of Bancorp Financial common stock outstanding and entitled to vote at the special meeting held by 213 holders of record.

Each share of Bancorp Financial common stock outstanding on the record date is entitled to one vote on each proposal and any other matter coming before the special meeting.

Voting by Bancorp Financial’s Directors and Executive Officers

At the close of business on the record