A beautiful piece with very nice details.
A rarer coin in this state of preservation.
Obverse: crowned eagle of the Russian Empire, initials on the sides of the tail, legend in the rim:
ЧИСТAГО СЕРЕБРА 4 ЗОЛОТНИКА 21 ДОЛЯ;
Reverse: in a laurel and oak wreath crowned inscription:
МОНЕТА/РУБЛЬ/1842/ С.П.Б.;