I can think of 2 things it might be. 1 would be a conversion bed for an early roadster to make it into a pickup, either factory or aftermaket. The other (this is the one I really think it is) would be a bed from a military (specifically Navy) spec '40-'42 Willys Americar Truck. I have been told that Willys built some of their trucks with a shortened bed to spec for use on bases.
