Military Payment Certificates, better known as "MPC's" were first issued in 1946 to servicemen of the American military. The earliest series were first used in Europe, then in Asia in areas where the USA maintained a military presence. The military brass realised that they were exchanging significant sums of foreign currencies for servicemen overseas, and that it was alleged that some was going into blackmarket economies. In an effort to stem blackmarket activities by servicemen, the MPC's were instituted, and were not exchangeable for cash outside of US military facilities. The first issues were rather plain, usually consisting of the heraldic eagle, and rather dull designs. After the conclusion of the Korean conflict a new series, Series 521 was issued, this issue was significant, in that in departure from the earlier drab designs, attractive females figured prominently on all denominations issued. This lovely Ceres was issued beginning in 1954, though it was printed in 1952, the first two digits in the series are the year the issue was printed, but not necessarily when it was used. This issue was used until 1958 when the Series 581 notes were issued. This Series 521 issue was significant also in that both sides of the notes featured attractive females. This $10 denomination would be the highest denomination in the MPCs until the Series 661 notes were released in 1968.