Your rifle has limited specific details that might help identify it. It seems like I can see a slight "fish belly" or convex curve in the butt's toe line, which with the longer two-screw tang, rules out a Leman rifle. The rifle is nicely stocked, but my guess is that it is a later rifle built from earlier parts including the barrel, lock, perhaps triggers, and probably assembled in the late 1850s or 1860s based on the condition of the walnut stock, flat front end on the cast pewter nose cap, and short barrel. You can argue the barrel may have been slightly shortened in this configuration based on spacing between the ramrod pipes, but if so, it was only a minor loss and the barrel was still short to begin with... which along with the smaller caliber and walnut stock suggests a later rifle. When I see a Pennsylvania lock plate, even when reused, I tend to place the gun in PA... but that's always a little "iffy."
Shelby Gallien