The UPU held an Air Mail Congress in Prague in 1931, which agreed to introduce a series of forms, etc., pre-fixed “AV” for AVION (Air). The AV2 form I have dealt with in my recent book, “The Postal History of Hong Kong 1841-1997”. However, the AV1 form was to include details of the routes, rates, etc., for each country and was published from 1933 from Berne. However, most British Colonies were excluded. The first Hong Kong AV1 was only issued at the beginning of 1940 and is given below: