It appears to be a English fowler (shotgun) AKA smoothbore. It doesn't look like it was converted from flint. The long heelplate, the checkering, and the large bow in the triggerguard points toward a sporting smoothbore fowler of British origin. The large bow might allow a gloved-hand to pull the trigger.
It looks like there is a "wedding band" on the barrel near the end of the forearm, and a sighting groove at the barrel breach. This confirms a fowler, having a half octagon/half round barrel. The forearm has been cut back from a full-stock as has the barrel, likely. The muzzle would have sported a soldered-on from sight. The barrel was probably around 44" to 48"" long. The barrel wedge and rear ramrod pipe look correct, based on what can be seen.
The proof mark "C" over "P" is the definitive barrel proof for shotguns and muzzle loading barrels, and the "V" mark is the "View" (visual inspection) mark.
Many 18th & 19th century fowlers were cut-down by gunsmiths to suit American customers needs & style.
