With a bit of gentle cleaning, you would see that the wood in the stock is of outstanding quality. The engraving that is there is of very good quality, and free of the typical "flying turnips" that are typical of early American guns. The barrels are very good quality damascus barrels.
That was not an inexpensive gun in it's day. It is further some of the earliest work of one of the most well respected, American double gun makers of all time.
Rare, isn't always valuable.
Best,
Ted