The coins in your wallet could secretly be worth tens of thousands of pounds each - here's how to know if you've got a really valuable one and how to sell it.
Small change has two values - how much it's worth when buying something, and how much it's worth to a collector.
For example, every 50p piece will buy 50p of goods, but some versions are worth much more to a collector because they are particularly rare or unusual.
One special Brexit 50p coin recently sold for £21,000 online due to its rarity.
How to tell if a coin is valuable
We have some bad news - most coins are only worth their 'face value' - for example 20p for a 20p piece.
But if a coin seems unusual in any way, look a bit closer, as that's the first sign that it could be valuable.
A spokesperson for coin experts Change Checker said: "Any coin that is of particular collector interest, perhaps it has a low mintage, a specific error or mis-strike detail, or its design carries a popular theme, may hold a higher value than others."
That could mean it has a special design on one side, or has an obvious mistake.
Change Checker has a guide that can help you work out if you've got a coin that's valuable to a collector or best spent in a shop instead.
The most sought-after coin right now is the Kew Gardens 50p, Change Checker said.
The scarcity index looks at the rarest 50 pence pieces, A to Z 10p coins and £2s currently in circulation.
Experts at Coin Hunter say the Kew Gardens 50p can sell for an average of £156 on eBay, but we’ve also seen some examples fetching up to £200 on the auction site.
The Royal Mint manufactured just 210,000 of the commemorative 50p coins to mark the 250th anniversary of the Royal Botanical Gardens in 2011.
Elsewhere, the most valuable 10p you may find in your pocket is the World Wide Web alphabet coin . One of these coins recently sold for £10.50 online.
In terms of £2 coins, top of the list is the Commonwealth Games Northern Ireland coin that we’ve seen sell for around £80 on eBay.
There are four different designs of the 2002 Commonwealth £2 coins - all are similar except that the central cameo features a different flag for the four constituent countries of the UK.
This coin represents Northern Ireland and there are 485,500 in circulation.
How to sell a valuable coin
If you have a good idea what your coin is worth, one option is to sell it online on auction websites such as eBay.
But if you'd rather leave it to a professional, members of the British Nuismatic Trade Association will be able to help and perhaps sell them on your behalf.
'Nuismatic' means 'relating to coins or medals', and you can find a list of these experts here , sortable by county to help find someone local to you.
