1881 "½" on 1s dull blue, type 3 surcharge from setting 3 (three varieties in a vertical strip, intended to be applied ten times to each 10x3 sheet), horizontal pair from pos. 2 (middle row of the sheet), "ERROR SURCHARGE DOUBLE", the spectacular variant with THREE impressions of the surcharge, two being in the normal positions while the third straddles the central perfs, affecting both stamps, fresh large part o.g. A truly extraordinary phenomenon, with no parallel in the 1881 surcharge series, caused by the sheet making insufficient progress through the hand press before the next application. From a single sheet which received eleven impressions of the setting, instead of ten. A great and famous rarity, ex Lilly and Charlton Henry and known to be unique in private hands. Only three such pairs existed, with pos. 1 in the Royal Philatelic Collection, and pos. 3 in the Tapling Collection at the British Library, as noted by Bacon and Charlton Henry in their 1936 supplement (p.3.) PF cert (1961), as Scott 8a.