An 1840 Penny Black Plate III imprimatur featuring the plate number will highlight Part IV of the Chartwell Collection, which will be held on December 12 in London.
It is the only plate number imprimatur from Plate III still in private ownership, making it highly sought after and warranting a high estimate of £150,000 ($240,428) at the GB Line-Engraved Essays, Proofs, Stamps and Covers sale.
Touted as a "highly important positional stamp of the utmost rarity" by the auction house, the bottom right "TL" corner margin specimen also features two extremely large regular margins, as well as an "…ove the Cement" margin inscription.
Its only detraction is some slight thinning caused by the fragments of a hinge.
The sale will also feature a rare £120,000-estimated ($192,336) 1840 Mulready One Penny Letter-Sheet, from May 1, the first day they went on sale, the same day as the Penny Black.
The British public quickly favoured the Penny Black, resulting in the withdrawal and pulping of the unused stationary. Remaining examples are consequently highly sought after, particularly those bearing the famed May 1 date, of which only four are known.
In comparison, a May 2 dated example, of which there are believed to be 18, has a £40,000 ($64,111) high estimate at the same auction, while one from May 5 is expected to achieve £10,000 ($16,027).
September's Chartwell Collection sale saw a rare set of 1940 Jersey stamps bearing a Nazi swastika overprint make £16,000 ($25,781).
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