When briefed by the Fort Drum EOD (Explosive Ordnance Division, they say 
they were started by the British UXO, necessity in that case the "mother 
of invention") one of the problems they had was with the soldier who 
thought to bring something along or home as a souvenir (once used 
extensively by the NYS National Guard, currently the permanent cantonment 
of the US Army 10th Mountain Division) and then decided against it, left 
in a hidden place in the barracks structure. They performed periodic 
sweeps to find said objects, and perhaps part of the story to some of the 
objects found concealed in buildings as a behaviorist might think.