A Papua 1930s-52 "STAMP DUTY / £100 £100" overprint with cancellation is the headline lot of Status International's August 21 online sale.
It carries an estimate of $18,600.
The stamp displays a Lakatoi (a local variant of boat), and is from a series that was first printed on the British portion of the island of Papua New Guinea in 1901.
The auction house comments that the lot is a "Great rarity with only several recorded, which actually makes it rarer than any of the rarest overprint errors or paper varieties of the postage stamps of Papua."
A Newfoundland 1927 60c De Pinedo stamp with a St John's cancel is valued at $13,950.
The lot was issued for use as airmail carried on a plane piloted by Italian aviator and avowed fascist Francesco Di Pinedo.
Only around 300 were ever printed, of which 33 are known to have survived. The auction house explained that the stamps are rare as "most were used on covers to dignitaries and officials in Italy (including to Mussolini), and around the world."
In January this year, a particularly fine example sold for $45,000 at Spink New York.
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