The set of stamps, Chile Airmails of Scott Type AP4 and AP9 were first issued in a series that ran from 1934-1939. A second unwatermarked series was issued 1944-1955, and a final series with different colors issued in 1951-1953.
In addition to the cataloged color and watermark varieties, there are also quite a few color variations and shades that are not listed in Scott or Michel catalogs.
Scott does include a note that states: “Nos C30-C50 have been re-issued in slightly different colors with white gum, The first printings are considerably scarcer.” No values are given however.
Below I am including some examples from my collection. Some of the color varieties are drastic and others are subtle shades.
I will let you be the judge.