Description
GB KGVI ½d deep green on illustrated envelope for the London Stamp Exhibition ‘One Hundred Years of Postal Progress’ 1837-1937, posted within London; with two added labels, ‘1937 all Empire Mails by Air’, ‘an Imperial Airways Empire Flying Boat’ & large blue label ‘London Stamp Exhibition 16-20 October 1937’, cancelled with the large violet cachet of the exhibition; a spectacular combination