Mario Gabelli runs GAMCO, an asset manager overseeing $10.41B in disclosed equity holdings (SEC CIK 0000807249). The latest portfolio (2025Q4) discloses 1036 positions across 11 sectors, with the largest positions in MLI, GATX and CR. On a mark-to-market basis the tracked portfolio has returned 21.8% over the past year. OpenStocks tracks 40 consecutive quarterly snapshots for this manager — every position change, new entry, and exit is logged below.