Yup, I miswrote, but edited my post within a minute of posting; I can't believe you and Mike were both able to catch me!

I wouldn't worry about the lack of nitro proofs as long as all other things[chamber length, walls, and bore condition] are OK.

It looks as if the snapcaps are indeed horn with German silver or plated "brass" I have a number of similar caps with other makers names on them along with a patent date etc. stamped into the horn. They are quite scarce, and IMHO classy.

Mal