Craftsman engines are generally Tecumseh and (less often) Briggs & Stratton. Craftsman doesn't make anything. All contracted out. Nothing different or unusual about them.
I have a Sears & Roebuck garden tractor engine made in 1947 and is actually a Briggs and Stratton model ZZ. About 130 lbs of cast iron, rated at 8 hp. It's just plain BIG.
Craftsman or Sears engines are sometimes prefixed with the number 500 after which follows the actual serial number which can be cross referenced back to actual engine manufacturer to determine model.