The 20p coin that's worth 350 times its face value

The rare undated 20p coin has been dubbed "the holy grail of change collecting" by The Britannia Coin Company of Royal Wootton Bassett after a printing mishap in 2008.

A rare 20p coin without a date on it has been called "the holy grail of change collecting" by The Britannia Coin Company of Royal Wootton Bassett following a printing mishap in 2008.

A small number of Twenty Pence pieces were struck without the year in November 2008 following a printing error.

The Royal Mint had 136 million Twenty Pence printed that year and, according to The Britannia Coin Company of Royal Wootton Bassett, only around 250,000 coins were minted with this unique error.

One seller in Stourport made a huge profit after they sold their mishap coin for £69.99 - almost 350x its face value.

The buyer also had free three-day postage.

The Britannia Coin Company of Royal Wootton Bassett, a coin-selling website, sells their 20p coins for £90.

The site explains: "The issue occurred because an old obverse ('heads') design was used with the new royal shield of arms reverse, introduced in this year.

"The previous Tudor rose design had the date on either side of the crown. When this was replaced with the shield, the date was moved to the other side.

"It was moved on most 20ps but not these ones, which bear no date at all.

"These coins have been circulated, so they will show the signs of wear typical of change that has been in wallets and cash registers.

"The only difference is this unusual error."