Kong. The new currency was gradually introduced beginning from July of that year. The yen replaced the complex monetary system of the Edo period in the form of Tokugawa coinage as well as the various hansatsu paper currencies issued by Japan's feudal fiefs in an array of incompatible denominations. The former han (fiefs) became prefectures and their mints private chartered banks, which initially retained the right to print money. To bring an end to this situation, the Bank of Japan was founded in 1882 and given a monopoly on controlling the money supply. Following the silver devaluation of 1873, the yen devalued against the US and Canadian dollars (since those two countries adhered to a gold standard), and by 1897, the yen was worth only about US$0.50. In that year, Japan adopted a gold exchange standard, defining the yen as 0.75 g fine gold or US$0.4985. This exchange rate remained in place until Japan left the gold standard in December 1931, after which the yen fell to $0.30 by July 1932 and to $0.20 by 1933. It remained steady at around $0.30 until the start of the Pacific War on December 7, 1941, at which time it fell to $0.23. The sen and the rin were eventually taken out of circulation at the end of 1953. Fixed value of the yen to the U.S. dollar No true exchange rate existed for the yen between December 7, 1941, and April 25, 1949; wartime inflation reduced the yen to a fraction of its prewar value. After a period of instability, on April 25, 1949, the U.S. occupation government fixed the value of the yen at ¥360 per US$ through a United States plan, which was part of the Bretton Woods system, to stabilize prices in the Japanese economy. That exchange rate was maintained until 1971, when the United States abandoned the gold standard, ending a key element of the Bretton Woods system, and setting in motion changes that eventually led to floating exchange rates in 1973. Yen and major currencies float By 1971, the yen had become undervalued. Japanese exports were costing too little in international markets, and imports from abroad were costing the Japanese too much. This undervaluation was reflected in the current account balance, which had risen from the deficits of the early 1960s, to a then-large surplus of US$5.8 billion in 1971. The belief that the yen, and several