Quite common. The late 1920's and early 1930s were the heyday for all sorts of philatelic commemorations. First/last days, openings/closings, anniversaries, etc., etc. Even more common is the "first day of 5 cent airmail rate" from a few years earlier.
June 5/6, 1932 was the transition date for 2 to 3 cent surface letters and 5 to 8 cent airmail. I picked these cover pairs from a dealer's $1 box several years ago (probably about what they are worth). Individually, each looks commercial, but as a group, their philatelic origin is clear.
Posted 02/19/2023 3:59 pm
