Hamilton H-31

The H-31 is an automatic chronograph movement manufactured by Hamilton and based on the ETA A08.231 (commonly known as the ETA 7750). Introduced in 2019, it remains in production and features a silicon balance spring along with a 60-hour power reserve—a notable upgrade over the standard 7750's 48-hour reserve. The movement is used in several of Hamilton's chronograph collections, including the Khaki Navy and Intra-Matic lines.