FN's internal firing pin safeties were introduced with late runs of the Mk II circa 1987-1988. (Initially runs of the Mk II did not have it nor did the "classic" style of Hi Power.) Some of the Mk III pistols didn't have them but the majority, actually desginated Mk IIIs, did. This would be around 1989.
This is what the bottom of the slide looks like if it does have the internal firing pin safety. If it doesn't have the milled opening at the rear with the end of the sear lever being a "paddle", it does not have an internal firing pin safety.