Great Britain 1872 1d black South Kensington Exhibition Proof Plate 27, SGDP36Great Britain 1872 1d black South Kensington Exhibition Proof Plate 27, SGDP36. A superb unused left hand marginal horizontal pair lettered 'QA QB' with four large even margins. Superb appearance and an exceptional multiple of this exceptionally rare special proof production of the penny black. In February 1872 official permission was granted to the printers, Perkins Bacon for the production of printed proofs on thick white card, imperforate from Die