The yen is Japan's official currency, with six types of coins and four banknotes. It is the third most traded currency globally, after the US dollar and euro, and is a key reserve currency. Introduced in 1870 during the Meiji era, the yen replaced a complex monetary system. In 1954, Japan stopped using sen and rin, making the yen the sole currency. Its value declined until 1971 but gained international demand from 1985 onward. Yen coins are designed to be distinguishable for the visually impaired and are made of aluminum, allowing them to float on water.