Undated 20 pence coins can be sold to collectors, traded or sold in online marketplaces, or sold back to the London Mint Office. To sell a coin back to the London Mint office, the London Mint Office must have previously owned it.
The undated 20 pence coin features a correct front printing of the Queen's likeness with an incorrectly printed back that is half solid and half lion print. Neither side has a date.
The Royal Mint notes that approximately 250,000 undated 20 pence coins were minted and released between 2008 and 2009. The coins are still legal tender and may be used as currency at their face value. Media attention to the coins greatly inflated the price in 2009. However, the reveal that so many of the coins were released has caused the availability of coins to potentially exceed the demand, driving down the price significantly.