Sweden’s Treskilling Yellow, one of the world’s most valuable stamps, is back in the ownership of an eminent philatelist after years in the hands of dealers, investors and banks.

Count Gustaf Douglas, a Swedish nobleman and politician, bought the unique 1855 error of colour by private treaty in May, and included it in a display to the Royal Philatelic Society London yesterday (October 31).

Deals surrounding the Treskilling Yellow have often shrouded in mystery in the years since 1996, when it set a world record for a stamp in being auctioned for $2.3m (more than £1.5m).

The buyer then was a consortium called The Box AB, which included Hans Lernestal and Tom Josephson. The stamp was later redeemed as a pledge to a Swiss bank, which in 2009 sold it to the dealer and investor Armand Rousso.

Previous owners have included Count Phillip von Ferrary (from 1894), King Carol II of Romania (from 1937) and René Berlingin (from the 1970s).

The used stamp is the only known example of the 1855 3sk stamp printed in yellow, instead of green. It was discovered by a schoolboy named Georg Wilhelm Backman in 1887, and removed from a cover believed to have been posted in 1857.

Douglas, the owner of the firm Securitas, is the 423rd richest person in the world, according to Forbes magazine. His display to the RPSL was one of the finest seen in Britain in recent years, comprising stamps, proofs, errors and postal history from all of the classic issues of Sweden.

Count Gustaf Douglas, the new owner of the Treskilling Yellow, at the Royal
Philatelic Society London on October 31, 2013