A nice, fully legible piece.
On the obverse the initials of Nikolai Grachev - St. Petersburg mincmaster.
Obverse: eagle of the Russian Empire of 1825 design, under it initials НГ, in the rim legend:
1828 ГОДА. МОНЕТА РУБЛЬ;
Reverse: in laurel and oak wreath crowned mint ordination information:
ЧИСТАГО/СЕРЕБРА/4 ЗОЛОТН./21 ДОЛЯ./С.П.Б.;
Edge: СЕР . 83 1/3 ПРОБЫ 4 ЗОЛ . 82 14/25 ДОЛИ;