"The Black Dozen" - Great Britain 1840 Penny Black mint block of 12 - SG2One of the crown jewels of Great Britain philately the largest known multiple from Plate 3 in private hands. Plate 3 is recognised as the printing plate which produced the finest impressions of the penny black. Great Britain 1840 1d black, plate 3, SG2 mint block of 12 known as The Black Dozen. This mint block of 12 Penny Black stamps is the largest known multiple from Plate 3 in private hands. Provenance from the esteemed Chartwell Collection.