After the Air Mail pillar box campaign of 1930-1938, the blue-painted boxes were recovered from the streets. The special double collection times plate holder was removed and replaced by a chunky single holder, the enamel Air Mail aperture flag was also removed (or painted over) and these boxes were then re-used as “ordinary” boxes. Not infrequently flaking red paint can reveal a peep of underlying blue—a sure sign of an ex-Air Mail box.