Nice rifle; thank you for bringing it here to be commented on, and admired. I would strongly suggest that you give us some better photographs of the full length, half views and detail images such that the folks here can make some valid observations on the rifle. The two dark, dark photos do not flatter your gun.
You have provided a number of microphotographs of some barrel marks that cannot be deciphered and may be nothing but file marks, when shots of the lock, box, breech, trigger guard and other details might help equally well, or better, in your search for information. Removing the barrel might reveal some marks on the lower flats, but that is not guaranteed. Some here would consider that three pages of pure speculation is useless and has been a waste of your time.
Dick