I have a Green River Rifle Works percussion rifle. I need help identifying what model it is. Serial 916 with .45 stamped under, so I am assuming one of the first 1,000. It's at my uncle's house, but I can get more measurements like LOP or Barrel Length. I know my uncle thinks it's worth something, but I am just trying to figure out what it is. Is this rifle desirable? Thanks in advance, I know I am asking a lot.