A nicely preserved piece.
Not described in Kaminski and Kurpiewski, a variant without rosettes at the Wieniawa coat of arms and without a dot after IOAN, only with dots in the reverse legend.
Obverse: eagle with wings upwards, on its sides initials C-G, in the rim legend:
IOAN CAS-D-G-POL-& SVEC-REX-;
Reverse: crowned inscription:
16.II.50/GROS:ARG:/DVP:REGN:/POLONI- and Wieniawa coat of arms.