To promote the new air mail postal services then available, in 1930 a number of letter boxes were painted blue and equipped with enamel AIR MAIL signage. In 1933 a special Type B (small) Air Mail pillar box was cast. It had a double collection times plate to incorporate air mail information. The scheme was short lived, ending in 1938; later many former or ex-Air Mail boxes were re-used on the street as ordinary pillar boxes.