1840 (April) "TO ALL POSTMASTERS." from the G.P.O. at Edinburgh advising of the new adhesives and envelopes, affixed at top-left with unused 1d. plate 1a, NE, good to very large margins; folded and with light overall toning but still fine and extremely rare. B.P.A. Certificate (1998) states "originally issued with a pair of 1d. blacks, presently bearing a single, Plate 1a, lettered NE, is genuine". S.G. Spec. PN1. Photo