Heavy Vehicle or Trailer Parts Box

I am not sure what this is out of, but it is certainly the spare parts and tool box for something on wheels as the contents labels deal mostly with axle parts. So it could be from a truck, car, tank, trailer, artillery piece or at gun, etc... It is very heavy duty. It has some holes in one side and some in the bottom, either where the box was mounted to something or where some internal dividers may have once been mounted to the box. There is a small grouping of about 5 little holes on one side that appear to be damage from something, which is surprising given the weight of this box. Very interesting box. I already consulted with a number of vehicle collectors and dealers and no one has seen it before. It would be a great piece for restoration. The box itself without any of the protruding bits measures about 15" x 3 3/4" x 7 1/2"