The United Kingdom from 1p to £1 were redesigned the undated 20p coins last year. The designs for the 5p and 10p had been unchanged for last 40 years and there is an oral rule that designs should be changed at least every 40 years to keep the currency fresh. The undated 20p coins designs usually not match with the change of monarch. The Queen has reigned for so long; the change had to be designed first. Though, this change to the currency has resulted in 'mule' coins escaping into flow.

Due to this, the mismatch involves the new design reverse side (tails) and the old design Queen's portrait side. Generally this would only result in some coins of 2008 being issued with an older date for example 2007 but with the creation of the new designs for the 2008 currency the date on the 20p was moved to the Queen's portrait side. The Queen's portrait side had no date on the old coins. So the result of this mismatch is not an undated 20p coins, it is a wholly incorrectly one.

The Royal Mint does not know exactly how many undated 20p coins were produced and released into circulation but it is estimated that the range between 50,000 and 200,000. The Royal Mint is anxiously searching their change for a mule coin issued in error by Coin collectors across the UK. In June of last year, up to 250,000 of the coins are revealed by the UK press, which lack a date on both faces, had been put into circulation.

The last time an undated 20p coins entered general circulation was over three hundred years ago. This is evidence to the excellence of The Royal Mint; the facility that strikes all Britain's circulating coinage, which is at the front position of casting technology the world over. Its stringent quality control procedures mean that errors striking such as the undated 20p coins are exceptionally rare in reality.

The undated 20p coins were the result of a minting error. The feature undated heads face of the 2008 Tudor Rose 20 pence piece and the undated tails face of the 2008 Royal Shield of Arms 20 pence piece. Since the news of the mistake hit the titles, auctions sites such as eBay have been flooded with listings for undated 20p coins. However, some of these cleverly worded schedules are in fact offering everyday 20p pieces, which are worth nothing more than their face value.
At last the new undated 20p coins to be worth anything they have to be undated on both sides. There are EBay sellers who are listing and shaping coins that are undated on one side. Everyone is talking about undated 20p coin right now this is not the actual, this is a normal 20p coin!