On a recent episode of Pawn Stars a gent brought in a 5th Model Burnside Carbine, which he sold to Rick for $1,200 (in excellent condition, it probably is worth about $2,500-$3,500). The other rifle, which Rick wasn't interested in appeared to be a Trapdoor Springfield, but with a thumbpiece that stuck out to the side more than normal, and had a round know on the end of it. I know there were a number of experimental models made, but can't find anything in my references. Anyone have any idea about it?