I think the 10 and 12 are probably the same. I've seen them on e-bay but i've also read a few complaints from those who've bought reproductions and the threads don't fit. The face must be fitted/filed in any event; it's a gunsmith job. If anyone might have originals it would be Jerry Andrews. I don't have his number available but you'll find his contact info by forum search. Mine have the bronze locking screws; earlier ones do not. This is the first one I've been unable to remove and I'm surprised at how stubborn it's been. Hopefully I won't break it.