WBurns;
operating purely from memory here but i believe the chamber marking of D=65/19.0mm would indicate a pre 1924 gun. This is chamber length & diameter of chamber just in front of rim seat & was used only on guns carrying notro proof from the era. Will dig out my proof book if someone else doesn't have their's handy. The bbls should weigh just over 2 3/4 lbs, by about a half ounce. Nice looking gun for its intended purpose.

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