Mexico 1968 Olympic Games postal cover double-signed by Tommie Smith & John Carlos the African-American athletes who gave the 'black power' salute as

Mexico 1968 Olympic Games postal cover double-signed by Tommie Smith & John Carlos the African-American athletes who gave the 'black power' salute as a political demonstration on the medals podium, signed in ink, Smith has inscribed World Record performance details achieved in 1967 & 1968