A very nice piece.
A rarer coin in this state of preservation.
Obverse: bust of Frederick to the left, in the rim legend:
FRIDERICUS WILHELM III BORUSS REX;
Reverse: crowned shield with the coat of arms of Prussia, on the sides the date 18-04, below the shield the denomination 4- GR-/B, in the rim the legend:
84 EX MARCH PURA COLON-;