This coin is 20 mm & 2.9 grams. The coin probably is too good to be true. 62% silver 37% copper. +-2%. There are very even die scratches on the reverse, and the coin has very rough edges
Definitely a fake. The weird fields on both sides (including the horizontal lines on the reverse) and the general style give it away. Makes me wonder if graininess was added to the dies themselves to convey an impression of weathered metal...