Korean currency
The yen was the currency of Korea during the Colonial rule, from 1910 to 1945, and was issued by the Bank of Joseon It was equivalent to the Japanese yen and consisted of Japanese currency and banknotes issued specifically for Korea. It was replaced by the South Korean won at par in 1945, and by the North Korean won in 1947.
North Korean won
As explained above, there are two varieties of foreign certificates. For the 1978 banknote series, foreign certificates, called "Pakkundon", meaning "exchangeable money" were implemented by an overstamp and serial number color. This was intended to protect the value of the national currency in North Korea's command economy. These were first released in 1983 in two forms, one for "socialist visitors" which had a red stamp, and one for "capitalist visitors" which had a green stamp. Another series was released in 1986 with either a blue or red Guilloché style stamp. These were issued in all denominations, except for the ₩100 note, presumably because it was assumed by the government that foreign visitors to North Korea would not show proper respect for its depiction of Kim Il-sung. These notes were discontinued in 1988 and replaced with a new series of Pakkundon in all banknote form that was more distinguishable and unmistakable from generic circulation currency.