Bed I.D. Please

Any ideas of what this bed is off of. Dimensions of inside box are approx. 57.5 L x 44.5 W x 13 D . Thanks

 

It looks more like a trailer box, perhaps military or industrial, than a pickup bed.
There are no fender mounting impressions or bolt holes on the side panels and the stock appearing tailgate has no brand name as would be found on civilian pickups.

 

Thanks pasadenahotrod. Anyone else care to weigh in. Thanks

 

I agree with him ^...the only other possibility that comes to mind is that there were some aftermarket beds intended for use in cars as an accessory (ala the Hudson offering, if memory serves me right). However, I think the box in question is too wide at 44 1/2".