You might post the question on The Muzzleloading Forum; they have a section dedicated to research and help in identifying muzzloading guns. This
link will get you to the forum, but you'll need to register to post. You can also use my personal referral link:
http://www.muzzleloadingforum.com/fu...eferral/10540/
Note that I get personal referral credits if you use the latter link.
Another option is to post the question on the American Long Rifle forum:
http://americanlongrifles.org/forum/index.php?
Both forums have lots of members who are expert in identifying old firearms.