As Lloyd said, this is a Dangerfield and Lefever gun.
It ended up selling for $1675.00 plus $60.00 shipping, which I felt was too much considering the overall condition. One hammer spur was poorly repaired, and the trigger guard tang appears to have a solder repair. The forend wood is uncheckered, not orignal, and a poor match for grain figure and color. The small wood patch behind the tang is cracked, suggesting the frame is loose in the stock. Right muzzle appears quite thin. Numerous other blemishess too, but it is over 150 years old. It does have rarity going for it though. The buyer is a longtime Lefever student, so it's going to someone who can really appreciate it, and perhaps restore some of the major warts. I'd start with the forend wood and the hammer spur...
The frame and locks are very different from some other Dangerfield and Lefever guns, so I believe there is a good chance this was a percussion conversion or maybe something started by Dangerfield prior to the partnership. He is listed as a machinist prior to partnering with Lefever, but not a gun maker.
