Greg: I believe the barrels are Stub Twist.
Stub Twist was used on quality guns 1820s-40s, then both Stub Twist and an early Laminated Steel into the 1860s (as nail stubs were becoming increasingly difficult to obtain.)
Crolle Damascus was available in the 1820s, but Two Iron large scroll 'English Two Stripe' was not in general use until the mid-1800s, and with Three Iron 'Oxford' and a later Laminated Steel were used c. 1850-1890s.
There is an English Damascus tutorial, mostly courtesy of Stephen Helsley here
http://www.picturetrail.com/sfx/album/view/20258609more pattern examples here
http://www.picturetrail.com/sfx/album/view/18059733
