This is the most common of the surcharged provisional stamps, 650,000 copies having been printed by the Canal Zone Press, Mount Hope. This stamp (Scott C5) was placed into service on January 1, 1930, when the twenty-five-cent airmail rate for letters to the United States was reduced to twenty cents. Many other rates were also reduced at that time, and consequently the 20-cent provisional is frequently seen on first flight covers. Of the stamps printed, all but approximately 11,000 were actually sold, with the remainders burned in 1932.
Most non-philatelic usages of this stamp are common because it was in use a relatively long time. Specialists, however, look for it in conjunction with more interesting usages such as registry, special delivery, and foreign airmail, including letters from Colombia by the local German-owned airline known as SCADTA. The airline brought mail into the Canal Zone for forwarding worldwide using the 20-cent provisional stamp. It was taken off sale on November 17, 1931, when the new Permanent Series was placed on sale. It continued in use for several years, however, as people depleted their remaining supplies.