The barrels are an interesting pattern called English Damascus Twist, Damas Anglais Coupe’ and (by Ferlach) Gebrochener Englischer Damast
It was also offered on the Colt Model of 1878 hammer gun, but I have not seen it, nor was it listed on later Remington hammer guns.
I don't know how the tube makers fabricated the patten, but it was apparently only one rod.

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