Mexico C417-C421 blocks/4

Mexico C417-C421 blocks of 4, MNH. Michel 1402-1406. Art and Science, 1973. Aztec calendar stone; Carlos de Siguenza y Gongora, 1645-1700, mathematician, astronomer; Francisco Diaz Covaerrubias, 1833-1899, topographer; Joaquin Gallo, 1882-1965, geographer, astronomer; Luis Enrique Erro, 1897-1955, founder of Tonanzintla Observatory.