If you will look a little closer top one picture, it has been converted to a breech loader. It works like a trapdoor. I have seen it there, but I don't know if it was a Hawken conversion or some other 'smith that did it.
The Kephart Hawken started the craze. He wrote about it.
The breech loader is marked " J. P. GEMMER PAT. PENDING ". There are 3 of those rifles known . I think GEMMER was trying to keep up with the changing times. And you are correct , the Kephart rifle is unmarked .That is why Kephart took it to a local gunsmith to verify that it was truely a HAWKEN rifle.