A nice piece.
Patina, tarnish.
Obverse: crowned eagle of the Russian Empire, on the sides of its tail the initials M-W, in the outer rim the legend:
ЧИСТАГО СЕРЕБРА 3 ЗОЛОТНИКА 15 3/4 ДОЛЕЙ;
Reverse: in laurel and oak wreath, inscription:
3/4/РУБЛЯ./5/ZLOT-/1839...;