Already checked it's M1 290 & M2 280, you swap over to reserve quickly lol, cant see any circlip groove in rear axel but is welded, there are no circlip grooves at the split pin ends, and no spare M1 engines laying round LoL, the engine No is one that I know nothing about, the story goes his grandad used it to mow the lawns with and his grandmother used to follow him up with a mower with a catcher LOL. some more pics.