An "incredibly rare" error by the Royal Mint has seen up to 200,000 20p coins issued without a year date - making them worth £50 each.
The coins are missing their 2009 stamp and are instantly valuable - and could become more so.

The last time an undated coin entered circulation was more than 300 years ago in 1672 when Charles II reigned.

The mistake happened last year when all our coins from 1p to £1 were redesigned.

The designs for the 5p and 10p had remained the same for 40 years with an unwritten convention images should be updated every four decades to keep them "fresh".

This interruption in the Royal Mint's usually excellent quality control has left coin buffs excited.

The mistake saw a "mule" - coin with mismatched sides - enter circulation.

The updated 20p was supposed to shift the date from the tails side to the head's side.

But between 50,000 and 200,000 coins were minted using the old version of the Queen's head which does not have the year date.

Now, The London Mint Office - a private company with no connection to The Royal Mint - is offering lucky owners of the odd coins a chance to cash in.

Nick Hart, coin expert and spokesperson for The London Mint Office, said: "The London Mint Office is interested in bringing the fun of coin collecting to a much wider audience.

"Mistakes like this not only fascinate people but also have considerable value increase significance.

"We believe this extremely rare error will certainly get the public looking at the coins in their pockets again and noticing the excellent new designs launched by the Royal Mint last year on our coinage."

People with an undated new 20p need to register their details with The London Mint before sending in the coin and claiming their reward.

Full details of how to register are available online at www.undated20p.com

This is not the first time Royal Mint has made a mistake.

In 1983 a new 2p was struck with the wording "new pence" rather than "two pence".

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