one who breaks open chests (cf. housebreaker, n.).

A thief who picks locks, or makes and uses false keys; (more generally) a burglar, a housebreaker; (also) spec. a safe-breaker.

a robber who uses explosives to open safes.

= safe-breaker n. at compounds 2a; (also) a burglar who is expert at opening a safe's combination lock.

Criminals' slang. A safe-blower. Now chiefly historical.

‘a safe-blower (Thieves' slang)’ (Cent. Dict.); also elliptically gopher.

A burglar or safe-breaker.

= peterman, n. 3b.

(a) a worker with tools; a toolroom worker; (b) Criminals' slang a lock-picker or (U.S.) safe-breaker.