Company: OSBC
Filing Date: 2025-04-23
Form Type: S-4
Source: 0001104659-25-037832
Chunk: 20

Company: OLD SECOND BANCORP INC
Filing Date: 2025-04-23
Form: S-4
Chunk 20
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 the implied value of the merger consideration payable for each share of Bancorp Financial common stock, which we calculated by multiplying the closing price per share of Old Second common stock on those dates by the exchange ratio of 2.5814 per share and then adding the per share cash consideration of $15.93.

| ​                 | ​ | ​ | Old SecondCommon Stock |   |       |   | ​ | ​ | BancorpFinancialCommonStock |   |       |   | ​ | ​ | CashConsideration |   |       |   | ​ | ​ | Implied Value ofOne Share ofBancorpFinancialCommon Stock |   |       |   | ​ |
|:------------------|:--|:--|:-----------------------|:--|------:|:--|:--|:--|:----------------------------|:--|------:|:--|:--|:--|:------------------|:--|------:|:--|:--|:--|:---------------------------------------------------------|:--|------:|:--|:--|
| February 24, 2025 | ​ | ​ | ​                      | $ | 18.08 | ​ | ​ | ​ | ​                           | $ | 46.67 | ​ | ​ | ​ | ​                 | $ | 15.93 | ​ | ​ | ​ | ​                                                        | $ | 62.60 | ​ | ​ |
| [•], 2025         | ​ | ​ | ​                      | $ |   [•] | ​ | ​ | ​ | ​                           | $ |   [•] | ​ | ​ | ​ | ​                 | $ | 15.93 | ​ | ​ | ​ | ​                                                        | $ |   [•] | ​ | ​ |

The market price of shares of Old Second common stock has fluctuated since the date of the announcement of the merger agreement and will continue to fluctuate from the date of this proxy statement/ prospectus to the date of the Bancorp Financial special meeting and the date the merger is completed and

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thereafter. The market price of shares of Old Second common stock when received by Bancorp Financial stockholders after the merger is completed could be greater than, less than or the same as the market price of shares of Old Second common stock on the date of this proxy statement/prospectus or at the time of the Bancorp Financial special meeting or any adjournment or postponement thereof