"This 1942 manual is published for the information and guidance of personnel using the 20mm aircraft gun materiel M1 and M2 and contains technical information requried in the identification, use, and care of the materiel."
The primary purpose of this catalog is to inform commanders of Active
Army and Reserve component corps artilleries, divisions, division artilleries,
field artillery brigades and battalions, FA AIT brigades, and maneuver
training commands and area...
The primary purpose of this catalog is to inform commanders of active and reserve compenent units of the instructional material tailored to their needs which will be available at the Field Artillery School in FY 1979.