postal use. The great complexity of the stamp issues of this period has been studied by philatelists in recent years, most notably by Follansbee in The Stamps of the Mexican Revolution 1913-1916. The twenties and thirties Stamps produced in the two decade period from 1917 to the mid thirties retained a conservative character similar to those of other countries including the United States. The stamps were engraved and had a standard format consisting of a frame with inscriptions surrounding a portrait of an historically important person, building or scene. In the mid-1930s, this staid format slowly began to change into a more varied concept with a more contemporary look. In 1934, a series of stamps was issued depicting ancient and contemporary Indians engaged in activities such as making pottery. The frames of each stamp differed noticeably and the central image sometimes crossed over onto the frame. The lettering began to take on a more modern aspect also, such as a distinct Art Deco font on the 1935 stamp illustrating Zapata. In 1934-1935, Mexico issued a series of airmail stamps depicting Aztec gods and symbols. The lettering on many of these was in a strong Art Deco style, and one stamp, the 5 centavos, was a borderless image of Aztec symbols mixed with wings, unlike any stamps Mexico had previously issued. Several Mexican stamps are illustrated in Art Deco stamps. The appearance of Mexican stamps took an abrupt and major change with the 1938 issue commemorating the 25th anniversary of the Plan of Guadalupe. This issue had a thoroughly "modern art" look with drawings in a contemporary Mexican muralist style, surrounded by bold, modern lettering. These stamps were only the second issue to be printed by photogravure, which thereafter became a common method for production of Mexican stamps. From World War II to end of the century A number of stamps were printed in the early 1940s with drawings or paintings of images in a bold, Mexican Art Deco style, in a large square format with a common appearance. Many of these were the artwork of Francisco Eppens Helguera, a Mexican artist whose images were used on numerous Mexican stamps in the late 1930s through the early 1950s. Eppens also created the small, but iconic, 1939 postal tax stamp depicting a man attacked by a giant mosquito, issued to raise funds to combat malaria. Beginning in the 1940s, Mexico issued a