The Twenty-cent Prexie
Sheet stamp use
Twenty cents was the airmail rate to and from Hawaii and the US mainland from April 21, 1937 until January 14, 1945.
This cover is postmarked Honolulu, December 3, 1941. From information given in The Last Flight Out: Seven Pan Am Clippers on the Eve of Pearl Harbor in the Congress Book 1997, it would appear to have gone out on the China Clipper flight of December 5, the last mail flight to reach the mainland before the bombing on December 7. It also is possible that it was carried on the December 4 flight of the American Clipper, if there indeed was any mail carried on that flight.