Several months ago a friend here in western PA let me snap a few photos of his "George Kopp" rifle. He bought it at auction many years ago. I had never seen a Kopp rifle with these characteristics, and it was a relatively small gun compared to other Kopp rifles I've seen, so I forwarded the photos to Bill Vance who publishes the OWR-CSA Newsletter.
He said this was indeed a late George Kopp rifle, typical of his post-civil war work. George had started using parts from catalogs in some of his later work, thus the "toilet seat" commercial patch box.