Currencies such as Meiji Tsuho (government note in Meiji Period) which was issued after the Meiji Restoration were inconvertible paper currency (paper currency which was not assured an exchange with standard money, such as gold and silver), and at that time, gold standard system was an international trend, so Japan also needed to issue convertible currency (paper currency which was assured an exchange with standard money).
明治維新以降に発行されていた明治通宝などは不換紙幣（主に金や銀の本位貨幣と交換が保証されていない紙幣）であり、当時は金本位制が国際的な流れで日本でも兌換紙幣（本位貨幣と交換が保障されている紙幣）を発行する必要性があった。