1. Breech-plug tang almost certainly is not antique. It is too thick. Old ones were forged, not machined from bar, and much thicker.
2. The lock panel looks new, old guns had a more narrow panel.
3. Drum is modern style.
Of #1 I feel certain. #'s 2 & 3 fairly secure opinion.
If you plan to shoot it, be nice to know who made the barrel. It might be an old gun, re-stocked with a re-breeched barrel,replaced drum, retained the antique lock. No idea whether trigger guard & butt-plate new or old. TOW stuff is, hopefully, copied from original designs.
Just one guy's opinion. Have collected for decades, made a few rifles but not An Authority.