Other ‘special currency’ has been used during wartime
War has been a motivating factor for making changes to currency for many reasons. During World War II, the U.S. government created “special currency,” which had distinctive markings, according to the Bureau of Engraving and Printing.
Hawaii notes, for example, had a “HAWAII” overprint on the face and back. If the enemy acquired large amounts of this “special currency,” it could be easily identified and considered non-legal tender.