2 bbl sets

[Dean Romig]

Hello Gordon, if they can be documented as original to the gun as it left Parker Bros. IMHO they probably add another 25% - 35% to the value of the gun. If it can be documented that the second set was made for the gun at a later date by Parker. Bros., again IMHO, then maybe they will increase the value by 15% - 20%... maybe a bit more.
It would be difficult, if even possible, to be able to document such a thing from Remington records.

[C grade]

I agree with Dean,especially on the guns that come from Parker with a second barrel. As Austin has documented, they are fairly rare and a lot of two barrel sets have "lost" the second barrel.
David