A nice, legible piece.
Obverse: bust of the Tsarina to the right, below her the mint mark СПБ, in the rim the legend:
Б-М-ЕКАТЕРИНА-II-IМП-IСАМОД-ВСЕРОС;
Reverse: eagle of the Russian Empire, on the sides of the tail initials, in the rim legend:
1766 МОНЕТА - РУБЛЬ-;