It may have started life as a Bantam T3 or Willys MBT (looks like it could have a T3 or MBT tub), but there may be a tailgate which opens up possibilities that it is a hacked WWII trailer, Bantam T3C or some other make entirely. The fenders are incorrect for a T3/T3C/MBT, and not in the stock T3/T3C/MBT location. Also, the axle does not appear to be T3/T3C/MBT (hubs are wrong).
We need better photos of the axle, tongue, coupler, tie down hooks,stake pockets (original or add-ons), rear of tub, etc. Otherwise, any responses you get will be pure guesswork.
Whatever it is and all things considered, $200 or so might not be a bad price for a platform to build on if the frame and tub are solid. However, if there is rust damage or on close inspection it turns out to be a hack job, best to pass on this one.