Great Britain 1918 3d violet "Postal due" (Harrison printing) imprimaturs, SGD5varGreat Britain 1918 3d Violet "Postal due" (Harrison printing) imprimaturs, SGD5var. Very fine unmounted mint, with full original gum, bottom marginal pair of imperforate imprimaturs, each stamp with a "BPMA" handstamp on reverse. Some light gum wrinkling as was prevalent across the whole sheet. A scarce philatelic piece. Exceptional provenance as they were released from the British Postal Museum Archives in 2014. Prior to this they were stored in the