This gun is incorrectly identified as a fowler. It has a full octagon barrel, cheekpiece, rifle front and rear sights, and a full patchbox. Note the thick wall on the barrel at the muzzle. It should be called a smooth rifle, or perhaps a "buck and ball" gun. It may have been a rifle originally, that was later bored out so that it could shoot shot. While most shot-type guns have single triggers, this gun appears to be from New York, or close to that area, where single triggers were very common on rifles. It should be called a "smooth rifle." The gun appears to date to the percussion era, based on the thin butt stock. While the percussion lock looks original to the gun, that aspect of a gun can be misleading unless given a full inspection with the lock removed.
An interesting detail is the attachment of the silver inlays along the forestock, wrist, and in the cheekpiece. Note there are no nail heads showing, indicating the inlays are attached by small pointed tabs soldered to the back side, that are pressed down into the wood. Henry Leman in Lancaster, PA, applied inlays in that manner at times, but it is not a common detail. The gun appears to be in nice condition, and is a good example of an eastern smooth rifle for the museum