100 Mk air-mail stamp, watermark 3 Y, imperforated proof into deep blue instead of deeppink colored printing ink in the on the right upper MARGIN CORNER BLOCK OF FOUR with full, very wide sheet margins of a brand of MINT NEVER HINGED, two with hardly, visible Anhaftungsspuren, the leftly lower one and the margins with small remainders of an hinge. An imposing and rare unity! Certificate Soecknick BPP "genuine and perfect"