I can't really tell if it is a replacement. The bridle has the bench fitting marks that look exactly like the ones on the frizzen and the lock. I would have just written it off as a replacement but for that small pair of file marks. I don't know why anyone fitting a replacement to the lock would have bothered to put the marks on. Fit and finish look similar to the other parts, but a well made 60 year old part won't look that different than a well made 210 year old part. If a replacement, why shape it so oddly? I could see it someone wanted to machine it out, but the angles aren't square, so it was files, and well filed at that.
I guess it fit's into the who knows curiosity category.
I am going to use the lock on a rifle that I build up, so it will probably be replaced anyhow.
Mike