This is a very accurate model of a Roger Bros. cable operated removable gooseneck trailer of about 1950. Rather than using a hydraulic ram to raise and lower the trailer bed during the unloading process, the ram was operated by a cable controlled by the tractor's winch.
The "geep dolly" or as Rogers calls it, a gooseneck dolly, is the same as that used in the Sheepscot kits 95046, 95047, 95048, and 95049 cast metal lowbed kits.
Here’s a company shop built trailer with some truss rods to help out with a little more capacity. The trailer is 36 feet long, interesting that the truck and trailer is about 55 feet long, over length on most of the eastern states in the 1950s.
The early 50s Autocar is set up for snowplowing in the winter and doesn’t do any long haul work