The lock plate fits the mortise well with good margins of wood around plate, so it may be the original plate. However, the current "flintlock" is a rebuilt lock with modern parts. The color and shape of the parts appear modern, but the most telling details are the screws which are modern made with machined flat bottomed slots, all with clean undamaged edges. Also note the cock screw has a flat tip, almost always an indication of a modern screw. There is a color mismatch between the plate and the parts, i.e. the cock, steel, & frizen spring are darker and all seem to have traces of a modern blue finish present between the rust spots. There also seems to be a stylistic issue between the cock and pan. The cock seems to stop on the top of the pan's rear shield rather than the top edge of the lock plate, in the style of a double-throat cock, while this is a single throat cock. I have never seen an original flintlock with these particular parts.
I believe this gun was an original percussion rifle and the current lock was inappropriately modified into a flint style lock using vintage reproduction parts from some years ago before they were as accurately reproduced as they are today. It is also possible the lock plate is not original, despite its good fit into the mortise...which if true would suggest it was close in size and shape and had only some fine reshaping/tweaking to properly fit it into the old mortise...which was a great idea so the original mortise wasn't badly chewed up. Shelby Gallien