Falkland Islands SG 48 Mint 1904-12 KEVII 1s sheet and cover

1904-12 1s brown, a complete sheet lacking the upper left corner stamp, brilliant o.g. (trace of hinge in margin and one stamp only, otherwise unmounted). Only 255 sheets printed and a remarkable item in its own right, but much enhanced by the presence of the missing stamp (sans margins) affixed to a large (260 x 210mm) official registered cover (embossed Arms on flap) and tied by type F4C 'FALKLAND / ISLANDS' cds, dated 'AU 5 10', with type 1 blue/white registration label at lower left and complemented by a m/s 'R' in circle in red crayon at upper right. The cover (which must be extremely rare as a commercial solo franking paying the quadruple 2½d foreign rate + 2d registration - Heijtz cat £600), addressed to the president of the Argentine Philatelic Society, contained this and several other sheets and blocks making up a £10 order, the original printed invoice for which (No. 1116) is also included. The official form, dated 2 August 1910, states '... for Stamps which I enclose herewith as enumerated below, part of which are on the Envelope'. A wonderful piece of philatelic history, and a quite extraordinary occurrence to have the stamp on cover along with the very sheet from which it came! - P256001393