This set of stamps features the unique 96c olive-bistre colour error right margin block of four with full original gum, superb centring and exceptionally fresh colour.
The block shows the original streaky gum associated with all stamps printed at this time. This gum is usually lost, if treated at all. There are two pencil marks on the margin which have been on the block for a long time, their origin is unknown.
The block also shows the variety error of watermark, which is centred unusually low, with the letters "C C" appearing above the crown and at the top of the stamps.
Without question the rarest and most important item of Hong Kong philately.
Only 48 unused examples have been recorded, including this block of four.
The block of four is the only unused multiple of the 96c olive-bistre. It is thought that only one other multiple exists - a used pair.
The unique block of four has rarely changed hands or been offered for sale. It has graced only the most important collections of Hong Kong.
A noted philatelist from New York, George Burghard assembled specialised collections of Hong Kong and early Switzerland. He sold the 96c olive-bistre block privately circa 1961. He signed the roll of Distinguished Philatelists in 1960.
Based on this latest sale price, and given the rarity of the single known block of four in existence, one could conservatively expect it to sell for upwards of HK$17.5m (Approximately £1.5m) should it appear at auction.