Really early roadbike engine from the looks of it, the earliest models I've had anything to do with have all run dynamos rather than magnetos. The basic shape of the engine is very close to the 50s/60s models except for the exhaust port & lack of cam on the end of the gearchange shaft for disengaging the clutch during shifts
Even my fathers 1954? Jawa 350 twin runs the dynamo, has the key & amp meter in the middle of the tank & fishtail mufflers but the basic engine shape remained the same until the late 60s or early 70s
