JCPhilately on Instagram: ""Rare Stamp Series: Episode 4 - World's Most Expensive & Rare Stamps" The Japan 1871 500 mon Centre Inverted stamp is a legendary philatelic rarity from Japan’s first stamp issue (the “Dragon” series). In normal examples, the denomination “500 mon” is printed correctly at the center; in this unique error, the central characters were accidentally printed upside-down, and only one copy is known to exist — making it the most important and valuable classic Japanese stamp a