Old Second Bancorp, Inc.
US ˙ NasdaqGS ˙ US6802771005

SecurityOSBC / Old Second Bancorp, Inc.
InstitutionNorthern Trust Corp
Latest Disclosed Ownership764,341 shares
Latest Disclosed Value $ 15,409,115
Northern Trust Corp reports 13.30% decrease in ownership of OSBC / Old Second Bancorp, Inc.

On May 14, 2026 - Northern Trust Corp filed a 13F-HR form disclosing ownership of 764,341 shares of Old Second Bancorp, Inc. (US:OSBC) valued at $15,409,115 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 17, 2026 disclosing 881,576 shares of Old Second Bancorp, Inc.. This represents a change in shares of -13.30% during the quarter. The current value of the position is $16,372,184 USD.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-05-14 2026-03-31 13F OLD SECOND BANCORP INC DEL COM 680277100 764,341 -117,235 -13.30 15,409 -10.36 0.0004
2026-02-17 2025-12-31 13F OLD SECOND BANCORP INC ILL COM 680277100 881,576 -116,322 -11.66 17,191 -0.34 0.0005
2025-11-14 2025-09-30 13F OLD SECOND BANCORP INC ILL COM 680277100 997,898 583,491 140.80 17,249 134.63 0.0005
2025-08-13 2025-06-30 13F OLD SECOND BANCORP INC ILL COM 680277100 414,407 -3,779 -0.90 7,352 5.65 0.0010
2025-05-13 2025-03-31 13F OLD SECOND BANCORP INC ILL COM 680277100 418,186 -28,959 -6.48 6,959 -12.48 0.0010
2025-02-14 2024-12-31 13F OLD SECOND BANCORP INC ILL COM 680277100 447,145 -15,767 -3.41 7,950 10.17 0.0011
2024-11-13 2024-09-30 13F OLD SECOND BANCORP INC ILL COM 680277100 462,912 -150,833 -24.58 7,217 -20.61 0.0012
2024-08-14 2024-06-30 13F OLD SECOND BANCORP INC ILL COM 680277100 613,745 12,456 2.07 9,090 9.23 0.0015
2024-05-14 2024-03-31 13F OLD SECOND BANCORP INC ILL COM 680277100 601,289 -36,373 -5.70 8,322 -15.48 0.0014
2024-02-13 2023-12-31 13F OLD SECOND BANCORP INC ILL COM 680277100 637,662 -6,209 -0.96 9,846 12.35 0.0018
2023-11-13 2023-09-30 13F OLD SECOND BANCORP INC ILL COM 680277100 643,871 3,802 0.59 8,763 4.83 0.0017
2023-08-11 2023-06-30 13F OLD SECOND BANCORP INC ILL COM 680277100 640,069 10,507 1.67 8,359 -5.56 0.0016
2023-05-15 2023-03-31 13F OLD SECOND BANCORP INC ILL COM 680277100 629,562 -19,492 -3.00 8,852 -14.98 0.0018
2023-02-13 2022-12-31 13F OLD SECOND BANCORP INC ILL COM 680277100 649,054 -37,350 -5.44 10,411 16.21 0.0022
2022-11-14 2022-09-30 13F OLD SECOND BANCORP INC ILL COM 680277100 686,404 -32,370 -4.50 8,958 -6.86 0.0020
2022-08-12 2022-06-30 13F OLD SECOND BANCORP INC ILL COM 680277100 718,774 130,574 22.20 9,618 12.69 0.0021
2022-05-13 2022-03-31 13F OLD SECOND BANCORP INC ILL COM 680277100 588,200 136,729 30.29 8,535 50.16 0.0015
2022-02-08 2021-12-31 13F OLD SECOND BANCORP INC ILL COM 680277100 451,471 123,867 37.81 5,684 32.87 0.0009
2021-11-15 2021-09-30 13F OLD SECOND BANCORP INC ILL COM 680277100 327,604 4,648 1.44 4,278 6.82 0.0008
2021-08-13 2021-06-30 13F OLD SECOND BANCORP INC ILL COM 680277100 322,956 -20,410 -5.94 4,005 -11.71 0.0007
2021-05-12 2021-03-31 13F OLD SECOND BANCORP INC ILL COM 680277100 343,366 -71,738 -17.28 4,536 8.21 0.0008
2021-02-11 2020-12-31 13F OLD SECOND BANCORP INC ILL COM 680277100 415,104 -21,344 -4.89 4,192 28.16 0.0008
2020-11-16 2020-09-30 13F OLD SECOND BANCORP INC ILL COM 680277100 436,448 -16,101 -3.56 3,271 -7.07 0.0007
2020-08-14 2020-06-30 13F OLD SECOND BANCORP INC ILL COM 680277100 452,549 83,773 22.72 3,520 38.15 0.0008
2020-05-14 2020-03-31 13F OLD SECOND BANCORP INC ILL COM 680277100 368,776 -1,896 -0.51 2,548 -48.97 0.0007
2020-02-14 2019-12-31 13F OLD SECOND BANCORP INC ILL COM 680277100 370,672 -13,551 -3.53 4,993 6.35 0.0011
2019-11-13 2019-09-30 13F OLD SECOND BANCORP INC ILL COM 680277100 384,223 22,013 6.08 4,695 1.51 0.0011
2019-08-13 2019-06-30 13F OLD SECOND BANCORP INC ILL COM 680277100 362,210 10,296 2.93 4,625 4.40 0.0011
2019-05-13 2019-03-31 13F OLD SECOND BANCORP INC ILL COM 680277100 351,914 -13,681 -3.74 4,430 -6.80 0.0011
2019-02-12 2018-12-31 13F OLD SECOND BANCORP INC ILL COM 680277100 365,595 14,445 4.11 4,753 -12.39 0.0013
2018-11-14 2018-09-30 13F OLD SECOND BANCORP INC ILL COM 680277100 351,150 -3,885 -1.09 5,425 6.12 0.0013
2018-09-18 2018-06-30 13F/A-1 OLD SECOND BANCORP INC ILL COM 680277100 355,035 8,908 2.57 5,112 6.23 0.0013
2018-08-14 2018-06-30 13F OLD SECOND BANCORP INC ILL COM 680277100 356,926 10,799 5,140
2018-05-09 2018-03-31 13F OLD SECOND BANCORP INC ILL COM 680277100 346,127 -302 -0.09 4,812 1.78 0.0013
2018-02-14 2017-12-31 13F OLD SECOND BANCORP INC ILL COM 680277100 346,429 7,999 2.36 4,728 3.87 0.0012
2017-11-13 2017-09-30 13F OLD SECOND BANCORP INC ILL COM 680277100 338,430 -1,412 -0.42 4,552 15.97 0.0012
2017-08-11 2017-06-30 13F OLD SECOND BANCORP INC ILL COM 680277100 339,842 3,732 1.11 3,925 3.78 0.0011
2017-05-12 2017-03-31 13F OLD SECOND BANCORP INC ILL COM 680277100 336,110 19,638 6.21 3,782 8.15 0.0011
2017-02-13 2016-12-31 13F OLD SECOND BANCORP INC ILL COM 680277100 316,472 3,719 1.19 3,497 34.55 0.0011
2016-11-09 2016-09-30 13F OLD SECOND BANCORP INC ILL COM 680277100 312,753 22,363 7.70 2,599 31.00 0.0008
2016-08-12 2016-06-30 13F OLD SECOND BANCORP INC ILL COM 680277100 290,390 7,791 2.76 1,984 -2.07 0.0006
2016-08-19 2016-03-31 13F/A-1 OLD SECOND BANCORP INC ILL COM 680277100 282,599 7,457 2.71 2,026 -6.07 0.0007
2016-05-13 2016-03-31 13F OLD SECOND BANCORP INC ILL COM 680277100 282,599 2,026
2016-02-12 2015-12-31 13F OLD SECOND BANCORP INC ILL COM 680277100 275,142 5,370 1.99 2,157 28.32 0.0007
2015-11-12 2015-09-30 13F OLD SECOND BANCORP INC ILL COM 680277100 269,772 269,772 0.00 1,681 0.0006
2015-08-13 2015-06-30 13F OLD SECOND BANCORP INC ILL COM 680277100 0 -35,149 -100.00 0 -100.00
2015-05-14 2015-03-31 13F OLD SECOND BANCORP INC ILL COM 680277100 35,149 315 0.90 201 7.49 0.0001
2015-02-12 2014-12-31 13F OLD SECOND BANCORP INC ILL COM 680277100 34,834 -51 -0.15 187 11.31 0.0001
2014-11-13 2014-09-30 13F OLD SECOND BANCORP INC ILL COM 680277100 34,885 -58 -0.17 168 -3.45 0.0001
2014-08-14 2014-06-30 13F OLD SECOND BANCORP INC ILL COM 680277100 34,943 -176 -0.50 174 7.41 0.0001
2014-05-14 2014-03-31 13F OLD SECOND BANCORP INC ILL COM 680277100 35,119 838 2.44 162 2.53 0.0001
2014-02-21 2013-12-31 13F/A-1 OLD SECOND BANCORP INC ILL COM 680277100 34,281 -100 -0.29 158 -19.39 0.0001
2014-02-12 2013-12-31 13F OLD SECOND BANCORP INC ILL COM 680277100 34,281 158
2013-11-13 2013-09-30 13F OLD SECOND BANCORP INC ILL COM 680277100 34,381 1,262 3.81 196 7.10 0.0001
2013-08-09 2013-06-30 13F OLD SECOND BANCORP INC ILL COM 680277100 33,119 33,119 183 0.0001
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.