It was not until the beginning of the Joseon period that copper coins called "mun" were minted for wide circulation. Jeohwa (저화/楮貨), which was made of standardized mulberry-bark paper early in the Joseon period, become the first legal paper money and was used as a medium of exchange in place of coins until it disappeared in the early 16th century. From the 17th century until the end of the 19th century, coins denominated in mun bearing the inscription Sang Pyeong Tong Bo (常平通寶) - the literal translation is "always exact coin" a reference to stable value - were the most widely circulated currency.