NOBEL PRIZE WINNERS: A rare multiple signed First Day of Issue Commemorative cover honouring the 100th Anniversary of the National Academy of Sciences, Washington DC, 1863-1963, featuring the signatures of eleven recipients of the Nobel Prize for Chemistry comprising Harold C. Urey (1893-1981; American Physical Chemist, Nobel Prize winner for Chemistry, 1934), Adolf Butenandt (1903-1995; German Biochemist, Nobel Prize winner for Chemistry, 1939), Robert Robinson (1886-1975; British Organic Chemist, Nobel Prize winner for Chemistry, 1947), Glenn T. Seaborg (1912-1999; American Chemist, Nobel Prize winner for Chemistry, 1951), Linus Pauling (1901-1994; American Chemist, Biochemist & Peace Activist, Nobel Prize winner for Chemistry, 1954 and Nobel Peace Prize winner, 1962), Vincent du Vigneaud (1901-1978; American Biochemist, Nobel Prize winner for Chemistry, 1955), Alexander Todd (1907-1997; Baron Todd, Scottish Biochemist, Nobel Prize winner for Chemistry, 1957), Melvin Calvin (1911-1997; American Biochemist, Nobel Prize winner for Chemistry, 1961), Dorothy Hodgkin (1910-1994; British Chemist, Nobel Prize winner for Chemistry, 1964), Robert B. Woodward (1917-1979; American Organic Chemist, Nobel Prize winner for Chemistry, 1965) and George Porter (1920-2002; British Chemist, Nobel Prize winner for Chemistry, 1967). All have signed in blue or black inks with their names alone to clear areas of the cover. Post marked at Washington DC, 14th October 1963. An impressive grouping of signatures. VG