The Type II 15-cent airmail (Scott C2) as it is commonly known, was issued without fanfare in March 1931. It was accomplished by surcharging 50,000 of the current 1-cent Gorgas regular stamps at the Canal Zone Press, Mount Hope. There are two major characteristics of this stamp. First, the basic 1-cent stamp is a definite yellow green, whereas the C1 Type I variety, which is far more common, is on dark green stamps. Second, and more definitive, is the shape of the "5" in the surcharge. On Type I stamps the top of the "5" is a horizontal stroke with a serif at the right rising up like a knob. However, on a Type II that horizontal stroke is a gentle curve with no serif.
The differences in scarcity and value of the two stamps is significant as it is believed the great majority of the Type IIs were used on regular mail and not saved since at first there was no recognition of the differences. In addition, most dealers who had already stocked up on the Type I surcharges were unaware of the differences and as result did not get involved in them until the remnants were turned over to the Philatelic Agency in 1932. The relative abundance of Type I is that it was the first airmail of this denomination and many thousands of them were saved after being used on first flight covers to a variety of Latin American countries, the rates to which were in many cases figured in 15-cent increments. In contrast, it is likely that many of the existing stocks of the C2 in collector or dealer hands are from that 1932 sale. It is significant that the number of first flights for them to be used on after 1931 was greatly reduced and the relatively few sold at Canal Zone post offices probably went out on commercial or personal letters that were not saved. Be that as it may, examples of the C2 Type II on any cover are truly scarce and greatly sought after by collectors.
It is believed that at least one-third of the 50,000 Type IIs were destroyed after stocks of the Provisional airmails were withdrawn from sale at Canal Zone post offices at close of business November 17, 1931, the day before the first permanent series stamps featuring the Spirit of St. Louis over Gaillard Cut were released for sale. On two occasions in June and October 1932 burnings of the 15-cent surcharged airmails totalling just under 19,000 stamps took place. From this known point estimates for the survival of C2 in any form are made. Since the C2 Type II was made due to the pending shortage of 15-cent airmails we can only surmise that the great majority of the burned stamps were indeed from their ranks.