Historical russian currency of a very small denomination is called

Ruble or rouble

Explanation:

The Ruble or rouble was used as a silver coin in the 1700s that is during the time of the Great Peter I before it was replaced from silver coin to a gold coin in the year 1897 by Soviet Union and Belarus.

Because of inflation the Ruble or rouble value later reduced in the year 1917 (that is during the time of of Russian Revolution) and this led to the formation of another unit of money as standard which is known as the chervonets.

Later, in the year 1947 the Ruble or rouble is then adopted again.