If this is anything close to what it is claimed to be, it should have Hudson Bay Co marks on the barrel, and George Goulcher and floral motifs on the lock. 24 ga., 88.3 cm octagon to round barrel. This would be a fine grade version of Bouchard's type 3.
Or, the lock is marked LONDON and has a "IA Tombstone Fox" stamp. 4" upper ramrod pipe, and a single number stamp on the breech. Military style butt plate. This would make it a fine version of the MOFT's "Most unusual Northwest gun."
I have never heard of such an animal, and either you have found 2 examples of a rare and rarely heard of gun, or somebody recently imported these from overseas. The former does not happen often, the latter does. There are many more fakes and misrepresented items on the market than rare ones.
I would recommend you contact the Museum of the Fur Trade and send them pictures. They will either wet their pants, or burst your bubble.
I hope it is the real deal, and the info gets published. That would be very cool.
:v
Ref's: Bourchard Les Armes de Traite.
MOFTQ: A Most Unusual Northwest Gun.