The original copper printing plate for the 1d and 2d 1847 Mauritius Post Office issue realised $1.1m at David Feldman in Geneva last night.
The issue was Britain's first colonial stamp.
That alone would make the stamps hugely appealing, yet it's the issue's scarcity that is the biggest selling point. It is among the rarest in the entire British Empire series, with only 27 survivors known out of an original run of 1,000 (500 of each denomination).
Mauritius was a tiny outpost of the empire and so stamps were not needed in large numbers.
A cover displaying both the 1d and 2d variants sold for a world record $4m at Feldman in 1993.
The plate went missing during the mid-1800s and only remerged in 1912, when it was hailed by the great stamp expert Alexander J Sefi as "the greatest Philatelic Treasure existing".
It then promptly disappeared into the seamy philatelic underworld. It surfaced a few times over the years, with its most recent sale taking place in 1968.
It realized $380,000 - then a world record for any philatelic piece.
The famous Bombay Cover, which displays two 1d Mauritius stamps, realised $2.1m.
Like the plate, it has been an object of desire for collectors since the inception of the hobby.