Yes, only the best will do. In fact, I would use star ruby for front bead.
I don't think Frankonia catalog will help. There are no std. parts on this gem. We're talking custom all the way. 
It was not that uncommon for original nipples to be Platinum lined...I hear there's a guy that goes to Friendship that Platinum lines them at a resonable price.
I was also told that big bore muzzleloading rifles were harder on nipples than front loading shotguns.
Your best bet would be to send your old crusty nipples to Dixie.
