My late 1960 C15 doesn't have an engine number anywhere I can see and have read that not all engines did. The only marks I can find is as per photo. Is that purely an inspector's stamp or does it mean anything?
That just looks like a qa stamp mate.
From somewhere on the net......
Engine numbers are usually by the crankcase mouth on the primary side. Exceptions are the Bantams which could be stamped on the front mounting point or just behind the crankcase mouth.
But maybe not.... :o