$2,019,200 The Baden 9 Kreuzer Error (German: Baden-Fehldruck 9 Kreuzer) is a remarkable postage stamp rarity produced by the historical German state of Baden in 1851. Baden’s first postage stamps were issued on May 1, 1851. Among them, the “9 Kreuzer Green” stamp stands out—a color misprint of the 9 Kreuzer denomination that was accidentally printed in green instead of the intended pink. The green color was originally meant for the 6 Kreuzer value, but due to a paper mismatch, the error occurred. Only three canceled copies and one unused copy of this error are known to exist. Remarkably, two of these copies are affixed to letters. The Baden 9 Kreuzer Error ranks among the greatest philatelic rarities globally. Interestingly, it remained undiscovered for 44 years after its issuance. (Getty Images)