i think the gloss in the side photo is flash from the camera,look at the photo of the inletting at the top tang, stock gloss looks normal in that shot.the pad is just a recoil pad which i didnt know was available at that time, but if he has the factory letter... those were very high grade guns made to compete even with the best from england. pres. grover clevland owned several including 2 custom made 8 ga.`s.
I have since seen other 1883 shotguns with this recoil pad. When I first saw it I didn't believe it to be of period. Now I believe it to be of period. The pads on the other guns are cracked and in poor condition.
I just purchased a 1878 Colt SXS 12 gauge with 30" damascus barrels, at no where near this price. My buttstock has a hard rubber buttplate with the rearing horse and the words 'The Club Gun". It is in very good shape and wish that I could post pictures of it, but I'm not that competent. Mine does not have the shine nor the red pads, but is in very good shape with shiney barrels.