A beautiful mint piece.
The coin is definitely rare in such good condition.
Obverse: eagle of the Empire of the 1844 pattern, between its legs and tail the initials M-W, in a rope border, in the outer border an inscription beginning with a rosette:
ЧИСТAГО СЕРЕБРА 4 ЗОЛОТНИКА 21 ДОЛЯ;
Reverse: in a laurel and oak wreath crowned inscription:
MOHETA/РУБЛЬ/1847;