A nice piece.
Patina, tarnish.
Variety with the ends of the legends PRVSS/PRVSS.
Obverse: in the pearl rim the eagle of Royal Prussia, in the outer rim the legend started with a five-petal rosette:
GROSS*COMV*TERR*PRVSS*153Z;
Reverse: in the pearl rim a royal bust wearing a crown and plate armor, to the right, in the outer rim a legend:
*SIGIS*AND*REX*AFTER*TO*TOCI*PRVSS;