Ken, if the gun were mine, I would write to the Cody Museum and pay the amount for the research of your gun. They will tell you if it came with an extra set of barrels or if the gun was sent back to the factory to have them made. Guns that came from the factory with an extra set of barrels are worth more than a set that came later on.
They might have the information to on who the gun was built for and where it was shipped to and the date of manufacture and of shipping.
http://www.bbhc.org/firearms/records.cfm
