Dave, You might get more responses if you post information about the barrel. I'd suggest posting the following information on the barrel so people here know what you have:
1. clear picture of signature (also good to have pic of muzzle and breech areas)
2. length of barrel
3. note any indications the barrel may have been shortened, such as moved barrel loops or odd/uneven spacing on barrel loops, any sign of the muzzle or breech being cut or altered in the past
4. bore size, is rifling still visible, number of grooves
5. outside diameter of barrel at muzzle, breech and middle.
Once people know what you have, they may be better able to help you with approximate dating, etc. Shelby Gallien