50 Cents Military Payment Certificate

Military Payment Certificates were introduced after World War II specifically to prevent black market currency manipulation — American servicemen were paid in scrip rather than dollars so that unauthorized dollar accumulation by foreign nationals could be controlled, and the series could be invalidated overnight with little notice. Series 591, which covers this note, was issued from 1961 and replaced during a conversion day in 1964, when unannounced exchanges gave black marketeers no time to redeem ill-gotten holdings.

Conversion days were typically kept secret until hours before execution. Anyone holding Series 591 scrip outside authorized channels found it worthless by close of business.