The copper plate used to print the ultra-rare 1847 Mauritius issue stamp realised $1.1 million at David Feldman in Geneva last week.
The issue was the first stamp the British printed for a region outside the British Isles, making it a hugely important piece of postal history.
In addition, it has one of the lowest printing runs of any British Empire stamp – with only 1,000 issued (500 of the 1d, 500 of the 2d).
Most were used to send out invitations to a ball held by the wife of the governor on the island.
In 1993, the famous Bordeaux cover (which features one each of the 1d and 2d denominations) realised a record $4 million.
So expectations were high for this copper plate, once called the "the greatest Philatelic Treasure existing”.
It’s been a hugely desirable piece since the hobby began and has only resurfaced a handful of times since its first sale in the late 1800s.
Since then it’s passed through some of the most prestigious collections in the world.
It even set a record for any numismatic item in 1968, when it realised a massive $380,000. That was also the last time it sold.
This latest sale cements the plate’s position as one of the world’s most important numismatic objects.
The sale also featured the Bombay cover, which displays two Mauritius 1d stamps. It sold for $2.1m.