Produced in 2002 by the Italian Mint, the coin was supposed to follow the standard format: small, lightweight, and featuring the Castel del Monte on the reverse side, but due to production errors, it has gained a value far above their face value.

In a very limited edition, a few were mistakenly printed with the diameter of 2 cent coins and an image of the Mole Antonelliana, which usually appears on the coins of higher value.

This error did not go unnoticed and was later found to be the result of deliberate tampering by a mint employee; while many were removed from circulation, some may still be out there. In 2013, the Italian company Bolaffi – specialising in rare item auctions – put six of these coins up for sale, with a starting price of €2,500 and one was eventually sold for €6,600, According to its director, these coins are seen as “masterpieces” of contemporary numismatics – not so much for their face value, but for their rarity and the history they carry. It’s unlikely, but one of these coins may have escaped authorities, so the next time you reach into your wallet, take a closer look.