Round exhaust port, piston nearly clears the intake window, 8mm mounting studs. I would guess cdh/zeda style. What are the rod markings and how many base gaskets does it have on it?
I meant base gaskets under the jug. I'll guess 2. Probably right on the fm80 rod. Also noticed the 40mm intake. It's almost certainly a early CDH or Zeda because of the phillips rather than allen head hardware.