A nuclear bomb arming-set switch. Possibly used on ‘tactical’ fighter aircraft.
‘ground-burst’ of a nuke from such a
small, low-flying aircraft would involve a ‘lay-down’ of the weapon with
a parachute and soft landing. A timer would delay detonation until the
aircraft had gotten a safe distance away. Always gets my imagination
going: cut to scene of elderly babushka lady cursing and beating with rake on H-bomb that has landed on her prize turnips.