On ongoing theme. Any stamp that commemorates space exploration. This does not include sci-fi related stamps.
colnect.com
Letter Rate 4¢ Package Rate 4¢ Postcard Rate 3¢ Effective 8/1/1958 United States 1/12/1962 Operation Ranch Hand Begins The United States Air Force launched Operation Ranch Hand in Viet-Nam. This operation was designed to expose transportation routes by killing the vegetaion around them. The most commonly used herbicide during this operation was Agent Orange. American President John F Kennedy (1/20/1961-11/22/1963) Argentine President Arturo Frondizi (5/1/1958-3/29/1962) Australian Prime Minister Robert Menzies (12/19/1949-1/26/1966) Austrian President Adolf Schärf (5/22/1957-2/28/1965) Bahamian Chief Minister Roland Symonette (1/1/1955-1/7/1964) Belgian Prime Minister Théo Lefèvre (4/25/1961-7/28/1965) Brazilian President João Goulart (9/7/1961-4/1/1964) British Prime Minister Harold Macmillan (1/10/1957-10/18/1963) Canadian Prime Minister John Diefenbaker (6/21/1957-4/22/1963) East German President Walter Ulbricht (9/12/1960-8/1/1973) German President Heinrich Lübke (9/13/1959-6/30/1969) Japanese Prime Minister Hayato Ikeda (7/19/1960-11/9/1964)