Bidspirit auction | British North America - Newfoundland

British North America - Newfoundland - Air Post stamps - 1931, Airplane and Packet Ship, large die proof of 50c in black, printed on paper without watermark, size 78x54mm, guide line at top, mirrored No.920 at upper left, no gum as issued, VF and rare, NSSC #AM8dp16, US$850, Est. $300-$400, Sc. #C7