[SchildaBrit]

Not S & S but S et S. Ought to be French, one might think. But I cannot find a single S et S in Stöckel. S and S is plentiful - in fact, too many to make a plausible identification. Anyway, it was surely not common for British/American gunsmiths to "Frenchify" their company names, although it did sometimes occur with German makers - e.g. the model train makers Märklin Bros. appearing as "Gebrüder Märklin & Cie." (Cie. as abbreviation for Compagnie). And as soon as I try German options, I end up with Sauer & Sohn in Suhl - surely a bit too early for them?

(S&S lock outside-REDUCED)

The lock does not have a bridle for the frizzen/hammer. Which suggests early 18. C. So the French-style ring cock is probably a replacement. The overall length is 14.5 cm, which looks like a small rifle/large pistol size. And it has a fly - just visible in the photo of the inside.

(S&S lock inside REDUCED)

My guess is that it's for a hunting or target rifle.

But who was S et S ???

P.S. Software says my photos are too large to upload. Will reduce resolution and retry

PPS OK photos reduced and uploaded.