I'm not yet qualified to say anything about the rifle since I am presently in an Entered Apprentice status in the study of these pieces, but I will make this one comment for whatever it's worth.
IMO the Masonic emblem is not period correct with the piece, and must have been added some years after the rifle was built. There is definately a "G" within the Square and Compass. The "G", which denotes Geometry as I pointed out in another Post recently, was adopted and included by the English Grand Lodge in 1832 and adopted by the American Grand Lodge a year or two later. Even with being adopted here in the States in 1833 or 34, it did not gain acceptance by the various State Grand Lodges and become commonly used until many, many years later. The late 1800's in some areas.