Jeff, I agree that the engraving at the front of the sideplate looks bolder and rougher - newer? Same for the tail, the two bits of C scroll and foliage each side of rear screw - and maybe the chip and dot border. I have not looked that closely at all details, and don't know if additional photos are available.
I am interested in further thoughts on where and when made, comparison with John Newcomer's work, other attributions and other research ongoing. This rifle is a very nice and complete package of profile, mounts and decoration. Bob