Twenty pence pieces were struck without the year by The Royal Mint in November 2008. The seller describes the coin as: "This rare 20p coin from the British Decimal Coinage is a must-have for any ...

An example of a rare undated 20p mule coin (Image: eBay/Getty/Vandervelden) As a result, the first batch of British coins with ... 450 times its face value. The 50 pence piece has become the ...