A nice piece.
Reverse illustrated in the catalog of D. Pączkowski.
Obverse: royal bust in laurel wreath, armor and cloak, with armor sleeve stripes visible, with Order of the Golden Fleece, to the right, in the rim legend:
IOAN-CASIMIR--D G-REX PO & S;
Reverse: crowned with a crown with jewels in a closed rim, with 5 rosette fleurons, a five-field escutcheon with the coats of arms of the Crown of the Kingdom of Poland, the Grand Duchy of Lithuania and the coat of arms of the Snopes of the Vasa dynasty, on the sides of the escutcheon the denomination marking 1-8, in the rim the legend punctuated by the coat of arms of Wieniawa Podskarbiego Wielkiego Koronnego Bogusław Leszczyński and the initials MW:
COIN-ARGE---REGN:PO-1651;