Below are Series 611 (used in Korea from 1964 to 1969) and Series 651 Military Payment Certificates (MPC) used in Korea in 1969 and 1970 when I was there. They sure bring back a few memories for me. US Military personnel were not allowed to have American greenbacks. The intent was to make it more difficult to black market and to limit the transfer of American money to Korean nationals. When the command believed that there was too much MPC in the possession of Korean nationals, they would withdraw one series of MPC and issue a new series. Korean nationals in possession of the old MPC were at a total loss.