Great Britain 1937 King George VI 2d. orange. Left marginal pair. Watermark upright. IMPERFORATE IMPRIMATURS FROM THE NATIONAL POSTAL MUSEUM. The word ‘Imprimatur’ comes from the Latin for ‘Let it be printed’ and applied philatelically to the very first sheet that was printed from an approved Plate. It was custom for the printers to begin the printing process of a new issue by printing six initial ‘test’ sheets. Once approved, one of these ‘test’ sheets was left imperforate, hand stamped ‘NP IMPRIMATUR’ on reverse and sent to the National Postal Museum for their archives. Superb unmounted mint condition. EXCEEDINGLY RARE AND IMPORTANT WITH ONLY 3 PAIRS AND 3 BLOCKS OF FOUR THAT WERE RELEASED INTO PRIVATE HANDS BY THE NATIONAL POSTAL MUSEUM IN 1984/85. AN IMPORTANT EXHIBITION ITEM. (SG Spec. Q10).