A nice piece of a very rare variety according to Anuszczyk's catalog.
Obverse: royal bust in crown, armor and cloak, in the rim legend:
D-G-AVGVSTVS-III-REX-POLONIARUM;
Reverse: crowned five-field escutcheon with the coats of arms of the Crown, the Grand Duchy of Lithuania and the coat of arms of Saxony surmounted by the Elector's mitre, girded from below by a palm wreath, on the sides of the wreath's branches the initials E-C, between the branches the denomination mark 18, surrounded by the legend:
SAC-ROM-IMP-ARCHIM-ET-ELECT-1756-;