unused Block of Four 6d. olive-green and light blue, a marginal block of four [21-22/26-27] with [22] showing "COIUMBUS" variety, fine mint. B.P.A. Certificate (1962). S.G. 169a, £600. Photo

Details
unused Block of Four 6d. olive-green and light blue, a marginal block of four [21-22/26-27] with [22] showing "COIUMBUS" variety, fine mint. B.P.A. Certificate (1962). S.G. 169a, £600. Photo