Even low-value coins like 10ps can be worth huge amounts of cash - and some are being sold for up to £11.
Most coins in circulation are not worth more than their face value - in this case, 10p.
But some can fetch far more when sold due to their value to collectors.
Rare designs on the reverse - or 'tails' - side of the coin can increase their resale value, as can limited numbers made or errors in manufacture.
For 10ps, some of the rarest are the 'A to Z' range from 2018 and 2019, the Sun reports.
As the name suggests, these coins each feature a letter of the alphabet, along with a design that represents that letter.
Have you got an alphabet 10p? Let us know in the comment section below
For example, the 'F' coin features fish and chips, while the 'N' one celebrates the National Health Service.
In 2018 there were 220,000 of each coin minted, according to cash experts Change Checker.
But when the coins were re-released in 2019, 20 of them had just 84,000 made, making them rarer and more valuable.
The remaining five 2019 coins were printed in runs of 83,000 for Q, 64,000 for R and 63,000 for W, Y and Z.
Here are the six rarest 10ps, as well as what they have sold for this year.
R - £14
This coin has a design featuring the robin redbreast.
The coin was the most scarce coin on the market in November, according to the latest rankings from Change Checker.
Y and Z - £11
The Y coin has a yeoman warder on one side - the famous keepers of the Tower of London.
Meanwhile the Z version features another British icon - the zebra crossing.
W - £10
This coin features a design celebrating an invention from Sir Tim Berners-Lee that is the reason you are reading this article - the world wide web.
Q and T - £6
The Q coin has a tongue-in-cheek design to mark another great British institution - queuing.
The T coin picks another common feature of British live - tea.
How to know 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.
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.
