The Eleven-cent Prexie
Sheet stamp use
The rate for a letter that was transported by air in the United States to a distribution point, then sent by surface transportation to Europe before being sent by air to its final destination in Europe was eleven cents for the first half ounce from November 23, 1934 until October 1, 1946.
Just as there was no separate rate for international airmail postcards until 1954, there did not seem to be a separate rate for postcards sent internationally by air-surface-air. This example is one of several in my possession that were sent to Latvia at the eleven-cent rate in 1939, although the others do not use a solo eleven-cent Prexie.