Lovely rifle there Fleener.
12 is the gauge, (bore), and I can only see the proofs apart form that. It looks in lovely order!
Fantastic bore. Roses were Birmingham barrel makers, a very large family. I've just been re-laying a rib and browning a 14 bore single barrel made by Roses. (Smith, Cornhill on the top flat.)
I have never seen a better bore, and congratulations on finding this one.
What is the rate of twist?
It will be for soft -skinned dangerous game. (Lion, Tiger and such) Made for firing a ball I believe. (More reliable stoppers than a conical ) I always regret not buying one similar when I had the chance in the early '80's. (Leeds arms fair)
Are there any markings inside the lock? It looks So clean, just about brand new!
Again, a lovely gun!
Richard.