W53 Warhead Arm/Safe Switch

This is the safety locking device on the Mk 53 Physics Package (Thermonuclear bomb) on display at the Pima Air Museum in 2018. It has only three settings: SAFE, FREEFALL, and RETARD. Rated at 9 Megatonnes, it was the basis for the B-53 gravity bomb (last ones dismantled in 2011), and the W-53 warhead for the Titan II ICBM. This one was meant for a B-53 gravity bomb carried by the B-52 long range heavy bomber. The markings show it to be: a W53, Type 3A, BA53-0, Ser No 889, P/N 163236-08 (9), ALTS 237W,264,275.