The 30-cent Gaillard Cut airmail stamp (Scott C12) was issued on July 15, 1941, and its original intent was to cover either a double weight or registered letter to the United States. The minimum registry fee at that time was fifteen cents. Other than this, it is often seen in combination with other stamps in 'make-up' rate situations. After April 1, 1945, when the basic airmail rate to the United States dropped to ten cents, it is found exclusively in these make-up rates. One of these is in combination with a 1-cent Gorgas stamp (Scott 105) on an airmail letter to Asia, Africa, and the Pacific, where the thirty-one cent airmail rate was in effect after July 16, 1951.
Some 30,500 of these stamps were overprinted between 1941 and 1952 for official use by Canal Zone-located federal offices. There are two types of overprints on this stamp known as 'The Official Overprints' (Scott CO5 and CO11).
First day covers of this stamp are quite common, and there are a large number of different cachets prepared to honor its issue by a variety of cachet artists. One could make an attractive exhibit of just these first day covers.