A nice, glossy piece.
An interesting mark on the after POLONI.
Obverse: in the pearl rim the coat of arms of Gdansk, in the outer rim the legend:
COIN:CIVIT:DANC;
Reverse: in the pearl rim a shield with a crowned eagle, in the outer rim legend:
KASIMIRVS-R-POLONI;
Silver, diameter 20.5 mm, weight 1.49 g.