Thanks for the information guys! What I took for a home made attempt is actually an early factory job then. That's cool! It makes it a nice piece of history in the development of the number 12s and the processes used at the factory to produce them. That's the sort of stuff I like to see. Neat to see how the MOP was shaped into such intricate shapes once they refined the process too. I would never have guessed at acid etching.
Rodney