Hi Bill,
Can't really tell much more than what you have. I doubt that the gun was rifled and still feel maybe it was reproofed in England, however if it was I think it should have barrel dimensions marked in gauge and not metric like Belgium did. I figure you're trying to tie it to the cotton gin Whitneys here in the US. It may have been a cape gun at one time with one barrel rifled for ball and the other smooth. Later it was rebored as a shotgun. Are there any indications along the ribs of a former gunsight?
Also try taking off the locks and look for any markings on the backside of the locks that could give you a clue to the guns origin. Though the barrels may be from Belgium, the rest of the gun may have been made in the US, hence the lack of proof marks.
Steve
