The Canal Zone Postal Service issued the 20-cent Pedro Miguel Locks-After commemorative (Scott 133) on August 15, 1939, as one of the high values in the Twenty-fifth Anniversary Series. The series includes eight 'before' and eight 'after' scenes of important Panama Canal installations.
The 20-cent depicts a view of Pedro Miguel Locks on June 17, 1927, with an Italian freighter at left and the SS President Polk, owned by the Dollar Line, at right. Taken from the control house situated between the two lock chambers, the shot looks beyond the hills (seen in the 18-cent stamp) into Culebra Cut.
Having very few actual postal uses, the 20-cent stamp was used on packages and in make-up situations in combination with other stamps.
The Bureau of Engraving and Printing produced 205,000 of these stamps, but just over half (104,000) remained unsold and were withdrawn from sale on February 28, 1941. Officials burned the remains on April 12 of that same year.
Like the other denominations of the Twenty-fifth Anniversary Series, the 20-cent was very popular with stamp collectors and first day cover enthusiasts. Like the others, collectors used it extensively on cacheted envelopes, which a large number of artists prepared. Other than on first day covers, it rarely appears on 'real' mail that collectors saved. It usually appears with other stamps to add value to the postage needed for a more 'exotic' usage such as a registered or overweight letter.