Very rare date.
Variety of 1/4 thaler coin from 1651, from the Posen mint, with a crowned bust on the obverse, with the inscription IOAN CASIMI DG REX POL & SVE M D L R P on the obverse and ARGENT on the reverse.
In the Shatalin catalog, the coin is specified as R6.
Weak strike.
Attractive coin with plenty of mint luster.