Commando Gearbox Shell?

Here are some photographs of the work I had to do to my gearbox shell, in order to make an Old Britts starter fit - obviously not the minimal fettling that was expected. My bike started its new life as a basket case (1974 850 Mk2a) and this gearbox shell seems to have a much more metal on the top lug than is standard and there are no numbers on it. Not all of the cogs it contained were Commando parts - one was suggested to be from a Dominator.







Simply for my own interest, is the shell likely to be a Commando part and if not, what?

Cheers, Bob