Great Britain 1841 1d red brown Plate 77 & 77b imprimaturs, SG8varGreat Britain 1841 1d red brown Plate 77 & 77b imprimaturs, SG8var. A superb unused matched pair of top marginal imperforate imprimaturs lettered 'AK' showing part sheet inscription. A remarkable matched pair taken from plate 77 which contained the "B blank" error on 'BA' and the corrected plate 77b which had subsequently had the "A" added. A rare and interesting philatelic pair. Plate 77 was registered on 19 April 1847, but probably not put to press