Derf00, it looks like you have a Stevens New Model Pocket Rifle, either First or Second Issue. The First Issue variant was made from about 1872-1875 with about 8,000 being made. The Second Issue variant was made from about 1875-1896 with about 15,000 being made. The main difference between the two was the First Issue had the firing pin was mounted on the hammer while the Second Issue had the firing pin mounted in the frame with a bushing. Hope this helps!
Steve Mace