3 institutions reported holding $3.6M of OCTAVE SPECIALTY GROUP INC (AMBC.WS) in SEC 13F filings for 2026-06-30. Largest institutional holders: SIMPLEX TRADING, LLC ($2.0M), GROUP ONE TRADING LLC ($1.1M), IMC-Chicago, LLC ($550,992). Source: SEC Form 13F.
| Rank | Institution | Value | Shares | Change |
|---|---|---|---|---|
| 1 | SIMPLEX TRADING, LLC | $2.0M | 312,600 | Added |
| 2 | GROUP ONE TRADING LLC | $1.1M | 181,000 | Trimmed |
| 3 | IMC-Chicago, LLC | $550,992 | 88,300 | Trimmed |
Source: SEC Form 13F filings · as of 2026-06-30