In January 2009 it came to light that a number of the new style 20p coins were minted without a date . This came about as the Royal Mint issued 2 different varieties of the 20p in 2008 . The first type had the Tudor rose on the Reverse (tails side) which was first introduced in 1982 the date was on this side divided by the rose.The obverse shows the Queen's head and the legend with no date . Later in the year the new type was issued as part of the new design for all the UK coins and shows part of the Royal arms. The Date was moved to the Obverse (heads side) as part of the legend. The no date error was the result of a mule i.e the obverse die from the first type was matched with the reverse dies from the second type. The Royal Mint estimate there are between 50,000 and 200,000 no date mules. THIS IS NOT RARE. In January 2009 the coins had a novelty value of around £100 but as more were discovered the value fell to under £20 until June 2008 the BBC reported the error then prices rocketed. In my opinion this will not last and any coin which has a mintage of up to 200,000 cannot be classed as rare especially when on just one day there were 210 listed on Ebay ! If You want Rare buy a 1934 Crown Mintage 934 value £3000 + or a 1951 Penny Mintage 120,000 at £40 Don't waste your money !