I think the proofmarks will be interesting, if it has any. I have seen a couple of Rival guns and , like Pete said, they were Crescent "looking". But, I think your gun is a bit different and maybe it's because it's so well preserved. I think the sculpting around the breech , the hammers, the metal to metal fit, and the metal to wood fit are better than the Crescents I have seen. It also has what looks like a gold shield in the bottom of the buttstock. I wonder if their were European "Rival" named shotguns, too.

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