50 Cents Military Payment Certificate

Military Payment Certificates were introduced after World War II specifically to prevent local economies from accumulating U.S. dollars — a problem that had fueled black markets across occupied Europe and the Pacific. Series 641, which covers this note, was issued to troops in Vietnam, Japan, Korea, Libya, and several other overseas stations simultaneously in August 1965, replacing Series 591 in a single-day "conversion" operation designed to strand any MPC that had leaked into civilian hands overnight.

Those conversion days were tightly controlled events. Soldiers had a fixed window to exchange old series for new; anyone outside a base at the time — or holding notes acquired through unofficial channels — was simply left holding worthless paper.