American astronomer (1906–1997) best known for discovering Pluto in 1930. Gemini-Titan II commemorative sheet, 8.5 x 11, bearing a First Day of Issue 1964 World’s Fair postmark. Sheet features an image of the Gemini-Titan II rocket displayed at the World’s Fair, as well as other space displays, and is signed under the image in blue ballpoint, “Clyde W. Tombaugh, Discovered 9th planet, Pluto, 18 Feb 1930.” In very fine condition. Earlier this year Pluto was ‘demoted’ to dwarf planet status. R&R COA.
