"BIRMAL" (cast inside the magneto chain cover) was a trade name used by the Birmingham Aluminium Casting Co. of Smethick, just outside Birmingham. Firms like this would have supplied many manufacturers (even some of the larger ones) with their castings, so other than pointing to a British make from the Midlands it doesn't help too much.
Am I seeing things, or does the exhaust valve stem miss the tappet? I can see that the inlet stem is off centre, but this was often the case.
Leon
