Octave Specialty Group, Inc.
MX ˙ BMV ˙ US0231398845
SecurityMX:OSG / Octave Specialty Group, Inc.
InstitutionSei Investments Co
Latest Disclosed Ownership66,718 shares
Latest Disclosed Value $ 519,061
Sei Investments Co ownership in OSG / Octave Specialty Group, Inc.

On February 13, 2026 - Sei Investments Co filed a 13F-HR form disclosing ownership of 66,718 shares of Octave Specialty Group, Inc. (MX:OSG) valued at $519,061 USD as of December 31, 2025. The entity filed a previous 13F-HR on November 13, 2025 disclosing 0 shares of Octave Specialty Group, Inc..

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.

Upgrade to unlock premium data and export to Excel .

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)
2026-02-13 2025-12-31 13F OCTAVE SPECIALTY GROUP COM NEW 023139884 66,718 66,718 519 0.0005
2025-11-13 2025-09-30 13F AMBAC FINL GROUP COM NEW 023139884 0 -23,565 -100.00 0 -100.00
2025-08-14 2025-06-30 13F AMBAC FINL GROUP COM NEW 023139884 23,565 4,689 24.84 167 1.21 0.0002
2025-05-14 2025-03-31 13F/A-1 AMBAC FINL GROUP COM NEW 023139884 18,876 -9,118 -32.57 165 -53.39 0.0002
2025-05-13 2025-03-31 13F AMBAC FINL GROUP COM NEW 023139884 27,976 -18 354 0.0004
2025-02-11 2024-12-31 13F AMBAC FINL GROUP COM NEW 023139884 27,994 -53 -0.19 354 12.74 0.0005
2024-11-12 2024-09-30 13F AMBAC FINL GROUP COM NEW 023139884 28,047 5,195 22.73 314 7.53 0.0004
2024-08-13 2024-06-30 13F AMBAC FINL GROUP COM NEW 023139884 22,852 -6,862 -23.09 293 -37.07 0.0004
2024-05-07 2024-03-31 13F AMBAC FINL GROUP COM NEW 023139884 29,714 6,879 30.12 464 23.40 0.0007
2024-02-14 2023-12-31 13F AMBAC FINL GROUP COM NEW 023139884 22,835 6,439 39.27 376 90.86 0.0006
2023-11-14 2023-09-30 13F AMBAC FINL GROUP COM NEW 023139884 16,396 16,396 198 0.0004
2022-11-14 2022-09-30 13F AMBAC FINL GROUP COM NEW 023139884 0 -23,950 -100.00 0 -100.00
2022-08-15 2022-06-30 13F AMBAC FINL GROUP COM NEW 023139884 23,950 -7,800 -24.57 272 -17.58 0.0006
2022-05-13 2022-03-31 13F AMBAC FINL GROUP COM NEW 023139884 31,750 4,600 16.94 330 -24.31 0.0007
2022-02-14 2021-12-31 13F AMBAC FINL GROUP COM NEW 023139884 27,150 0 0.00 436 12.08 0.0008
2021-11-12 2021-09-30 13F AMBAC FINL GROUP COM NEW 023139884 27,150 0 0.00 389 -8.47 0.0008
2021-08-06 2021-06-30 13F AMBAC FINL GROUP COM NEW 023139884 27,150 4,300 18.82 425 10.97 0.0009
2021-05-12 2021-03-31 13F AMBAC FINL GROUP COM NEW 023139884 22,850 0 0.00 383 9.12 0.0010
2021-02-08 2020-12-31 13F AMBAC FINL GROUP COM NEW 023139884 22,850 -3,200 -12.28 351 5.41 0.0009
2020-12-04 2020-09-30 13F/A-1 AMBAC FINL GROUP COM NEW 023139884 26,050 -1,900 -6.80 333 -16.75 0.0010
2020-11-06 2020-09-30 13F AMBAC FINL GROUP COM NEW 023139884 26,050 -1,900 333 801.7900
2020-08-17 2020-06-30 13F/A-1 AMBAC FINL GROUP COM NEW 023139884 27,950 7,800 38.71 400 60.64 0.0012
2020-08-11 2020-06-30 13F AMBAC FINL GROUP COM NEW 023139884 22,950 2,800 495 1,342.7138
2020-05-14 2020-03-31 13F AMBAC FINL GROUP COM NEW 023139884 20,150 -2,800 -12.20 249 -49.70 0.0009
2020-02-06 2019-12-31 13F AMBAC FINL GROUP COM NEW 023139884 22,950 -2,900 -11.22 495 -1.98 0.0015
2019-11-12 2019-09-30 13F AMBAC FINL GROUP COM NEW 023139884 25,850 0 0.00 505 15.83 0.0013
2019-08-14 2019-06-30 13F AMBAC FINL GROUP COM NEW 023139884 25,850 13,500 109.31 436 94.64 0.0014
2019-05-15 2019-03-31 13F AMBAC FINL GROUP COM NEW 023139884 12,350 12,350 224 0.0008
2018-08-03 2018-06-30 13F AMBAC FINL GROUP COM NEW 023139884 0 -14 -100.00 0 0.0000
2018-05-11 2018-03-31 13F AMBAC FINL GROUP COM NEW 023139884 14 -297 -95.50 0 -100.00
2018-02-08 2017-12-31 13F AMBAC FINL GROUP COM NEW 023139884 311 280 903.23 15 1,400.00 0.0001
2017-11-06 2017-09-30 13F AMBAC FINL GROUP COM NEW 023139884 31 17 121.43 1 0.0000
2017-07-31 2017-06-30 13F AMBAC FINL GROUP COM NEW 023139884 14 14 0 0.0000
2017-05-05 2017-03-31 13F AMBAC FINL GROUP COM NEW 023139884 0 -95 -100.00 0 -100.00
2017-02-02 2016-12-31 13F AMBAC FINL GROUP COM NEW 023139884 95 95 2 0.0000
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.