I just got in a nice G grade 16 gauge Parker and it has a couple things I'm not sure of. First there is an obvious plugged hole in the breech end of the barrels on the rib (see photos). I've included two photos so you can see it up close and see that the matting was definitely cut after the plug was put into the rib. There is only one plug on the rib.
Second, there is P.S. stamped on the barrel flats. Does anyone know what this stands for?
Third, when measuring the barrels I find both barrels measure .666 for the bores with .020 and .033 constrictions. Minimum barrel wall thickness on one barrel is .021 and the other .025. These are only in one area of the barrel with most of the barrel being well above .025. The thin areas are about 6 inches from the muzzle so I know there is no danger from pressure. Would these figures be unusual from a gun in serial number 193XXX range.
Thanks in advance for your help!