I just got something very similar to that only mine looks like a really tall dolly with some casters out front and a really big lifting plate that gets jacked up with a ram/chain combo. The guy said it was an ordnance lift from Ft. Ord.
Built it many years ago , to lift a large printer. Used the screw out of an old bumper jack. Very handy when it has the trans/engine attachment on it or to just lift up things to a level comfortable to work on. Joseph36