A mis-struck new £1 coin made the headlines last week after allegations it was a forgery were debunked. It’s great news for the man who found the faulty coin, as pieces with minting errors can actually be worth a pretty penny! Read on to discover what other mis-struck coins you might find in your change, and could make you a mint.

In 2005 the Royal Mint released a commemorative £2 to mark the 400th anniversary of that fateful 5th of November when Guy Fawkes tried to blow up the Houses of Parliament but was caught and jailed. The Mint was trying to be clever by printing the famous verse on the edge, but the ribbing on the coin clashed with the Rs. The coins appear to read “Pemember, Pemember the Fifth of November” instead of “Remember, Remember” – now they fetch up to £15 on eBay.

In 2015, the Mint launched a WWI Royal Navy design for the £2 coin. Shortly after, it was noticed that some of the coins appeared to feature a waving flag on the top mast of the ship design, while others didn't. The Royal Mint insists that it’s not a design error, but that occasionally debris can get caught between the die and the coin while striking, according to the Change Checker blog. It’s a simple mistake, and these coins fetch around £20 on eBay.

At the end of 2008, the Mint admitted to producing around 250,000 20p pieces with no date on them. The error occurred because an old ‘heads side’ was used with a new design ‘tail side’ which meant there was no year on either side. There are still quite a few of these in circulation, and if you find one they could be worth £200.

In numismatic jargon a mule is a coin struck with the wrong die (stamp). In 2014, around 17,000 commemorative £2 coins for the ‘Year of the Horse’ were struck with the wrong die, meaning they were lacking its 'cogged' or 'denticled' rim design, and featured a smooth rim instead. Some 38,000 of these coins were struck in total, so it was a big error. These coins are highly sought after, and can be worth as much as £175.

To celebrate the London 2012 Olympics, the Mint released a series of 50p coins with 29 different designs. A limited edition commemorative set of 29 goes for around £40 on eBay. But the original swimming coin is worth over £1,000 on its own. That’s because of a minting error that caused the swimmer’s face to appear covered with water. Only a few were made and it was quickly pulled from circulation, but some are still out there, so check your pockets!

Before 1981 all 2p coins had the words New Pence on them, rather than the current Two Pence. But in 1983 the Mint accidentally struck a small batch of the new coins with the old New Pence design on them. They can be worth up to £400! But beware: some eBay sellers are trying to pass off standard 1981 New Pence coins as the rare 1983 mis-struck ones, but these are only worth face value.

Several 1971 'silver' 2p pieces have been discovered lurking in small change and have fetched up to £1,350 at auction. 2p pieces are usually copper coloured, but in this instance copper-nickel rather than copper blank was left inside the minting machine by mistake, producing a small number of silver coins.