The 20-cent Canal Zone Seal and Jet airmail (Scott C-45) was part of the initial six stamps of this long-lived series. Originally intended to be used on letters to various foreign destinations, it later saw extensive use on mail to Latin America.
Of the 2,440,000 copies printed, all but ca. 150,000 were eventually sold. Those 150,000 were burned in 1980.
As with the other stamps of the first group, the 20-cent Canal Zone Seal and Airmail is often found in combination with the other stamps of the series on first day covers. Other than these, it is most often seen on letters to Latin America, but it is seen much less frequently in combination with other stamps or in multiples on any variety of usages.