Oooo, nice double!
As far as I can tell the finish on this Snider is original. It isn't marked as to maker, but it does have the typical "Snider Patent" with <==S==<< arrow mark on the top of the breechblock. It has two sets of proofs, a British set of 1868 rules marks on the underside of the barrel and a later (1890s?) set of Belgian proofs along the left side of the barrel at the stock line near the breech. The bore is absolutely pristine!
The load it likes is 70 grains of Fg, a couple of 24-gauge wooly wonder wads and a paper-patched 500 grain swaged bullet from Russ at Montana Precision Swaging, all put up in turned cases cut to the chamber by Dave at
http://rockymountaincartridge.com/ The bullets are not hollow base Minie style and therefore use no plug. They're not exactly cup based either like a typical PP bullet usually is - they have a small 'dimple' in the center of the base and I cut the patches so that they end up with no twisted tail, they just fold flat over the bullet base.
'Pan size' is about right for this yearling bison, leastwise a Montana-sized pan...

Yum!