My guess is shipboard watch standers, probably on submarines. The armory on subs is usually a locked cabinet in the stbd side aft, in the engine room. Pretty small cabinet as space is tight.
Submarine watch standards are prone to drop guns overboard, hull is round and once dropped, over the side it goes.
Cant tell you the number of time I sent the shipyard divers to retrieve a dropped overboard side arm. The got pretty good at it.
Usually a bored 19 year old playing with the weapon !