The RWB Auctions staff member told The BBC: '20p coins are a fixture in our change ... produced for the 2012 London Olympics ...

A demonstration of the different coin combinations which make 20p. Several coin values are shown before they morph into different combinations of coins which make up the same value, helping ...

As it is so unusual it has meant the coin has been dubbed the "holy grail" of change collecting making it much sought after. The 20p coin was highlighted on Instagram by Coin Collecting Wizard.