Kansas City, MO, Air Mail Field duplex handstamp
This duplex marking device was used to cancel mail at the Kansas City, Missouri, Air Mail Field (AMF). An AMF is a mail sorting facility located at an airport. Air mail dispatched from a city is taken to the AMF for sortation and distribution to outbound flights. Pouches labeled to the AMF from inbound flights are opened, and letter packages are dispatched to appropriate connecting flights.
Air Mail Fields were renamed Air Mail Facilities after the Post Office Department was reorganized into the United States Postal Service. Clerks at AMFs were under the jurisdiction of the Railway Mail Service prior to 1949 and under the Postal Transportation Service between late 1949 and the mid-1960s. They were managed by the Bureau of Transportation after 1960. Because the letters "RMS" or "PTS" do not appear between the canceling "killer" bars, this device was likely manufactured after 1960.