Great Britain 1924 1d Scarlet (Waterlow printing, Watermark Sideways), SG419a varGreat Britain Unused 1924 1d Scarlet (Waterlow printing, Watermark Sideways), SG419a var. A superb quality unmounted mint full original gum imperforate top marginal horizontal pair of imprimaturs from the sideways coil printing with "BPMA" (British Postal Museum Archives) handstamps on reverse. Imprimaturs represent the first stamps printed from the approved and finished printing plate and are highly desirable. A scarce rarity in uncirculated