Something's not right and I'm not sure what it is. Perhaps the lock tail and face don't go with 3 cross pins, maybe the threads look wrong, why has it got a dog catch and half cock, why aren't I seeing 300 years shrinkage where the back pin goes through? Why can't I find him in Stockel?
If I'd bought it I would pull that pan screw with trepidation, suppose it was UNF?
First thing I'd do is run my finger down the guns belly and feel for overhang on the butt plate, should be a good 1/8"