I would think it's a Buddhist 'monk' amulet, to bring prosperity/good luck. I don't think it's possible to put a reliable date on these kinds of things and the portraits may not be of anyone in particular for whom there is a particular period. The portraiture and workmanship definitely isn't characteristic for the 1700s though. I would say it's like not earlier than the mid 1800s. The pics are too out-of-focus to read the inscriptions but they're highly likely to be generic messages of promise about the fortunes of the wearer. I can't even see what language it is, but more often than not these kinds of medallions are from what was Siam (now Thailand).