I think Tom nailed it!
It does look like it started life as a Scamp
, but possibly only as a shell.
See those numbers on the door, especially the "15" at top right? I'd bet that's just one of a fleet of rental fish shacks that were scattered around some frozen lake every winter. The "frame/axle" is an obvious add-on to make it a "trailer" again...if in fact it ever WAS one. I don't know how such shacks were/are moved around frozen lakes, but skids seems more likely than wheels.