The rifle appears to be made in the percussion period, based on its single lock bolt, thin butt, pointed toe, and later rounded cheekpiece. The lock plate fits reasonably well, except for a slight gap at back, so hard to say if original, or replacement sometime along the way. A fascinating detail is the forward, smaller hole in the toe plate. It may be for a vent pick, and it seems like a small piece of a wire pick can be seen at the hole's surface. That hole, and what appears to be a bit of wire, need a closer look, and may show it was originally flint, although still made well into the percussion era.
If the gun were originally a flint, it would have been a double-throated type cock that did not require a clearance cut in the stock wood above the top edge of the lock plate, which your rifle does not have. However, the stock wood immediately behind the breech on the lock side of the tang does not appear to have as much erosion/dry rot from the caps' fulminate salts as would be expected from an original percussion rifle... kind of supporting a flint beginning.
I'd suggest taking a very hard look at that smaller hole in the toe plate that may be a vent pick hole, and may have a wire pick still in it, so you know what is there.
As to the current percussion hammer, the gap in size between the tumbler shaft and hole in hammer base seems too large in size for me to believe the hammer was originally fitted to this lock. More likely someone replaced an earlier hammer with a poorly fitted hammer with oversized hole, and tried to make it work... in more modern times.
I saw that rifle sell and thought what a great gun it was, to get a signed, full-stocked South Carolina rifle that's almost as rare as hens' teeth.
Shelby Gallien