POST OFFICE GREEN PAPERS NO. 23, 42 AND 45. Three pamphlets with detailed and excellent information and fascinating pictures reference "AIR MAIL OPERATION" (No. 23), "AIR MAIL" (No. 45) published 1939 and "INTERNATIONAL POSTAL SERVICE (No. 42) published 1938. These papers were issued primarily for the information of the Post Office staff and give its officers up to date and accurate information on various aspects of Post Office work. Unusual. (Ref 101746).