The paper-money in circulation is inconvertible, but has a forced currency. The notes represent 100 rubles; 50 rs., 25 rs., 10 rs., 5 rs., 3 rs., and 1 ruble, and are plainly stamped with their value.
1868, “Russia: Introduction”, in Handbook for Travellers in Russia, Poland, and Finland, 2nd edition, London: John Murray, page 45