A rare undated 20p coin released in 2008 by mistake when the new design was introduced (stock photo) This makes it extremely valuable for collectors.

Lifestyle Rare coins 'Never underestimate loose change' as rare 20p sells for 622 times face value People joked online that they "gotta start checking their pockets" after the unique coin sold for ...

The rare Royal Mint 20p coin inspired a mini bidding war amid collectors on eBay, prior to selling for almost £125.

And one recent online sale has drawn even more fascination to physical currency - a rare Royal Mint 20p coin, described as "very nice and interesting," which has sold for more than 620 times its face ...