Military payment certificates, or MPC, was a form of currency used to pay U.S. military personnel in certain foreign countries. It was used in one area or another from a few months after the end of World War II until a few months after the end of U.S. participation in the Vietnam War – from 1946 until 1973
As with any currency condition is everything, I would guess yours would be woth around $10.00. Worth hanging on to if you collect.