The 20-cent Gaillard Cut stamp (Scott C11) of this series is one of the originals issued on November 18, 1931. It was first intended for airmail letters to the United States and some Latin American countries. Its greatest period of use was from November 18, 1931, to November 30, 1937, after which date the rate to the United States dropped to fifteen cents. Like the other Gaillard Cut airmails, it is often seen in a 'make-up' rate situation. Some 3,214,000 were shipped to the Canal Zone, making it one of the more common stamps and on cover.
Between 1941 and 1952 some 30,500 of these stamps were overprinted for official use by Canal Zone-based federal offices. There are two types of overprints on this stamp known as 'The Official Overprints' (Scott CO4 and CO10).
First day covers are fairly scarce, apparently due to the relatively high face value of this stamp during the Great Depression. A good number, however, were used on letters destined for the November 25, 1931, Lindbergh flight from the Canal Zone to Miami. It is also frequently seen in combination with other stamps. Two of these are with a 1-cent Gorgas stamp (Scott 105) to make up the twenty-one cent rate to Europe, and less often for a thirty-one cent rate letter to Asia, Africa, and the Pacific after July 17, 1951.