The coins were made of untreated platinum ( 97 % ) .
The coins were were minted from 1828 to 1845 with denominations of 3 , 6 , and 12 rubles .
The coins were made of untreated platinum ( 97 % ) , and were minted from 1828 to 1845 with denominations of 3 , 6 , and 12 rubles .