Korean yen
The Korean yen was the currency of Korea between 1910 and 1945. It was equivalent to the Japanese yen and consisted of Japanese currency and banknotes issued specifically for Korea. The yen was subdivided into 100 sen. It replaced the Korean won at par and was replaced by the South Korean won and the North Korean won at par.
List of licensed and localized editions of Monopoly: Africa and Asia
The currency used in the game is shown with the letter "M" crossed by two horizontal lines. This is not the real currency of the Republic of Korea.