An unusual accidental dateless version of the 20 pence was reported to be in circulation in June 2009, the first undated British coin to enter circulation in more than 300 years. This was the result of the production of a mule, i.e. A version of the coin with a non-standard combination of obverse and reverse face designs. The fault occurred as a result of the 2008 redesign of UK coinage, which moved the date on a 20 pence from the reverse to the obverse (Queens head side), and a batch of coins were produced using the tooling for the obverse of the old design and the reverse of the new design. The Royal Mint estimated that between 50,000 and 200,000 entered circulation before the error was noticed. The Royal Mint stated these coins were still legal tender, although due to their rarity, the London Mint Office, a private company specialising in unusual coins, offered £50 to people with one of the mules, in the hope of selling them on to collectors for a higher price
