Korean currency
In 1902, won was introduced as the official currency unit replacing yang at 1 won = 5 yang. The bank of Korea was established 1909 but soon after in 1910, Imperial Japan annexed Korean Empire. Under Colonial rule, the country was made to use the currency unit "yen" in the name of Korean yen, which took over the Korean won at par. After the division of Korea, the state of South Korea was established and recognized in 1948, and won was again made the official currency of the new state. "jeon" was made the subunit of the currency that divided it into 100 equal parts. Bank of Joseon issued the currency for independent South Korea for the first time that too in banknotes only.
North Korean won
The won was revalued in November 2009 for the first time in 50 years. North Koreans were given seven days to exchange a maximum of ₩100,000 (worth approximately US$40 on the black market) in ₩1,000 notes for ₩10 notes, but after protests by some of the populace, the limit was raised to ₩150,000 in cash and ₩300,000 in bank savings. The official exchange rate at this time was around $740 but black market value of the ₩150,000 was estimated to be near $30. The revaluation, seen as a move against private market activity, wiped out many North Koreans' savings. "The Times" speculated that the move may have been an attempt by the North Korean government to control price inflation and destroy the fortunes of local black market money traders. The announcement was made to foreign embassies but not in North Korean state media. Information was later carried via a wire-based radio service only available within North Korea.