The 13 would mean that the bore was .710 from Greener, and as Roy stated anything over .719 would be out of proof. Does it have on the top of barrel in oval- Patent Treble Wedge Fast. On rib: St Marys Square, Birmingham, England Winner at all Gun Trials 1875-1891.
This gun is referred to as: 16 guinea Facile Princeps F 16 with machine engraving on action. (engine turned)
I have one similar, circa 1892 that has the above and is a 12 ga with 27 1/8" barrels that weighs 6 lbs even. Great to shoot if I could only get used to the safety.
