I have a couple of thoughts.... maybe they'll spark some better ideas from some of the other members.
1. My first thought was that it was some part of a sharpening jig, the kind you roll at a set angle along a sharpening stone.
2. My 2nd thought is that it clamps to a bench, with the wheels up.
3. That Craftsman lettering is from around the 1950's. I'm mostly looking at the "S" with the flat top & bottom, like a backward "Z". For example, AA has a picture of a JH Williams made Craftsman 8" adjustable wrench with that lettering with "PATD IN USA". The patent date was 1955. I suppose that could put that adjustable into the 70's? I'll need to check the catalogs.
Chilly