Yen was originally introduced by the Meiji government 1871. The new currency was a replacement for the complex monetary system based on Mon. The yen was legally defined as 0.78 troy ounce (24.26 grams) of pure silver and 1.5 grams of pure gold. The same amount of silver is now worth about 1181 modern yen, while the same amount of gold is worth about 4715 yen.