It’s reasonably well known that the UK Kew Gardens 50p is one of the rarest coins that you can find in your change, and they command a collector’s price which is hundreds of times higher than the coin’s face value. But did you know there are lots of coins that are even rarer that you should be looking out for?

There are also intriguing errors too. For instance, consider the BU 1983 UK coin set. It might seem like a fairly ordinary brilliant uncirculated coin set but examine one coin in particular. When the UK went decimal all the coins were titled ‘New Pence’ or ‘New Penny’ to the top of the design to differentiate the decimal editions from the pre-decimal coins. However, from 1982 the ‘New’ tag was dropped so each denomination read as one penny, two pence, five pence and so on.

By 1983 all the coins therefore should read as their individual denomination. But have a look at the Two Pence coin in this set. It says ‘New Pence’. How did this happen? This is an example of a ‘mule error’. Two dies are used to strike a coin: one for the obverse (heads) side and the other for the reverse (tails) side. A mule coin is created when the wrong die was used to strike one half of the coin. So in this case, the old ‘New Pence’ reverse die was used to strike these 1983 Two Pence coins. This mistake is what caused the undated 20p coin and the Lord Kitchener mule £2 coin too.