I am not any type of expert, but I did sell such a rifle this year for the family of a friend who had passed away. The rifle I sold was an over and under octagon barreled .45 calibre, it had a hammer on each side, and double triggers. The lower barrel was fired by a long nipple, it was in shootable condition, but was pitted. I sold it along with five more half-stock rifles for $100.00 each. I had dragged them around to gun shows and dealers since 1998, and this was the best offer I had gotten. Do try to read the printing on the rifle, it may have been owned by or built by someone famous, otherwise, I would advise you to keep the rifle, maybe someday rifles of this type will bring what they are really worth. Joe W. Smith, author of BLESSED ARE THE PEACEMAKERS, Civil War in The Ozarks.