As another of the most sought-after British stamps, the “Plate 77 Penny Red” is lauded for its rarity and unique backstory involving a printing plate that was never officially approved.

The stamp, dating back to 1851, went for $619,500 at a Robert A. Siegel sale in 2018. The buyer was a wealthy pharmaceuticals executive named Arthur Przybyl. Plate 77 Penny Red stamps were ...