Stepney

Hello, all! First post here. Worked out a deal on this old timer.. I have no idea who built it. Markings on front of the deck say "SP 24" which to me stands for 'self propelled 24" cut'. Which .. well, it is. Engine is an H50 Tecumseh which may or may not be correct. To me the mower looks older than the 70's engine. It has an unusual friction drive. The blade spindle moves up and down with a locking bolt to set the blade height. The deck is staggered like an old lawn boy, but in the opposite direction. The drive and spindle remind me of an old snappin turtle, but that's about as far as I can figure. The only name is on the ribber tire for the drive. "Davidson" is what it seems to say. Any idea who built this job? A Google archive search shows SP24 as models from Gemco, Toro, and Western Tool & Die. However none of those models look anything like this machine.