By Levi Winchester A rare 20p coin has sold for almost £60 on eBay because a massive design area which means the date is missing. This error coin is known as an “undated“ or “mule” 20p and there are thought to be thousands that were accidentally released into circulation. Error coins are particularly valuable to collectables. The massive flaw was caused when the Royal Mint changed its design back in 2008, and the date that is minted on the coin was moved from the back to the front. But in some cases, the old die was accidentally used – meaning some coins were released with no date on either si…