Great Britain 1938 4d blue Postage Due imprimaturs, SGD43varGreat Britain 1938 4d Blue Postage Due, SGD43var Imperforate Imprimatur Pair A superb unused unmounted mint with full original gum horizontal pair of the 1938 4d Blue Postage Due issue, as a rare imperforate imprimatur. These stamps originate from the National Postal Museum Archive and bear the "NPM IMPRIMATUR" handstamps on the reverse marking their official status and exceptional provenance. Extremely rare in this format. Provenance: Ex. National