JB;
Nice looking old double. That gun has much the same configuration as the W Richards I mentioned, except the W Richards has the lever on the left. Shape of locks, rounded action bar, hammer shape etc are all very similar. Your gun is I would guess of a bit higher original quality than my Richards & in much better present condition from what I can see in the pictures. My Richards had the bores proofed as a 14 but it precedes the chamber mark which was introduced in 1887. It does currently have 12 gauge chambers.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra