Looks pretty good from here, nice quality gun with pretty good browning, and case colors. I have a number of muzzle loaders from that era. I would want to know the actual bore diameters and the wall thickness. Good bores tend to mean "honed" given the gun's age.
Case certainly looks to be of the right time period, although label is a replacement (as you said). I would say 2 to 4 grand, though the small size of the market means that appraisal and actual sale can be disparate, or at least slow to move.
I would recommend looking up Vintagedoubles.com Kirby had a few guns in the same ball park, and of course, they have prices (he's in Eastern Washington State). You could also peruse Henry Krank in England for prices on what he has in stock.
