Great Britain 1951 2d pale red brown imprimatur, SG506varGreat Britain 1951 2d Pale Red Brown, SG506var A superb unmounted mint, with full original gum, imperforate imprimatur horizontal tte bche gutter pair in pale red brown. A remarkable and rare philatelic item originating from the National Postal Museum Archive, with the NPM IMPRIMATUR handstamp on the reverse confirming its provenance. An exceptional rarity as these tte bche formats were never issued for public use and is preserved in uncirculated