The only unused multiple of the rare 1865 Hong Kong 96c olive-bistre postage stamp is to cross the block at Spink on January 17.
It will provide the highlight of a Hong Kong sale of Chinese stamps and covers, with a valuation of $838,612.
The issue was released in early 1865, but was printed in the wrong colour.
It remained in use for a brief time until it was withdrawn in August 1865 - when the correct stamps left the printers.
Today only 48 copies of the stamp survive across a variety of grades. The lot's status as the only unused multiple should attract the world's foremost collectors.
Spink explains: "This is, without question, the most important item of Hong Kong philately. No other block or cover, despite their rarity, can compare with this block…
"In 1865, when this stamp was released, stamp collecting was in its infancy; the first printed stamp album was only produced in 1862. This 96c. olive-bistre stamp was missed by most collectors and dealers.
"Naturally the issue of this stamp was not advertised by the Hong Kong Post Office, as it was associated with the embarrassing 'variation' of colour."
Investment-minded buyers may also be fighting for the stamp come sale-day.
The global stock market has opened poorly in 2016, with Chinese stocks falling by 7% on the first day of trading. In contrast, the market for leading Chinese stamps has traditionally offered stability, achieving steady growth of 10.7% per annum between 1989 and 2014.
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