A set of four 1933 Swaziland official overprint stamps are valued at £30,000-50,000 ($45,401-75,669) ahead of a sale at Spink London.
The lot, one of only four sets known, will headline the May 18 sale of Peter van der Molen's award-winning Swaziland collection.
Spink explains: "In 1934 the Administrations of Basutoland and Swaziland arranged for ½d., 1d., 2d. and 6d. duties of their current issue to be overprinted "OFFICIAL" by the Union Government Printer in Pretoria, for use on official correspondence.
"When the Secretary of State for the Colonies in London heard about these issues, which had not been authorised, instructions were given to withdraw those stamps.
"While in Basutoland a total of 137 stamps had already been used from 24 May until 25 June 1934, in Swaziland it was stated that only two or three letters to the Colonial Office in London had been franked with these "OFFICIAL" overprints, however none has ever been found."
Both sets of overprints were swiftly destroyed, but rumours persisted over the years that four sets of the Swaziland issue were still extant.
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