SOUTH AUSTRALIA SGO83 Official 1899 2 1/2d indigo O.S. opt Block of 4

Official. 1899-1901 2 1/2d indigo type O3 O.S. opt lower marginal block of 4 brilliant o.g. (three stamps unmounted). Trivial marginal blemishes but most attractive with lovely colour. Scarce. Purchased from Stanley Gibbons (still on their card)