When a previously unknown, historically important coin comes up for auction, collectors, dealers and even auctioneers are prone to a little over-excitement. When four such coins are involved in a single lot the anticipation can go off the Richter scale.

Such a scenario is possible in the London auction rooms of Spink on Thursday, Sept. 27, when a unique 1868 Hong Kong proof set is to be offered for sale. It consists of a proof dollar, half-dollar, 20, 10 and 5 cents struck at the defunct Hong Kong Mint.

The set of five silver coins was acquired over 100 years ago by the present owner’s family in the former British Colony. The set has never previously been offered on the market. Until now there was not even a hint of a rumor that such a set existed. Its appearance is both remarkable and totally unexpected being struck at a time the mint was scheduled to close.