Mexico. Charles III of Spain. 1760-1788. 38.6 mm, 23.83 g, 12 h). Mexico City mint, Struck 1779 . ·CAROLUS·III· DEI·GRATIA· // [177]9, laureate, draped and cuirassed bust of Charles III right, seen from behind / ·HISPAN·ET IND·REX· o/M ·8 R·F·F·, crowned arms of Spain between pair of columns draped with a ribbon on which is inscribed: PLVS - ULTRA. KM 106.2. Good VF Details, lightly toned - sea-salvage piece with large area at rims of both sides deeply corroded; holed or hole begun at 11:00 Rx. .
Despite only final "...9" of date being legible, this must be 1779. In 1769 the mintmaster's initials were "MF" rather than 1779's "FF". Also the bust of Charles didn't replace the globes and pillars obverse until 1773