So take a look at our guide to the most valuable 50p pieces below - and next time you're paying in cash, just check exactly what you're handing over first. Here's coin exchange website ChangeChecker's list of the ten rarest 50p piece designs in general circulation.
1. Kew Gardens
Only 210,000 of these coins were ever minted, making it the rarest 50p piece - indeed, it's the rarest British coin in general circulation. Some Kew Gardens 50p pieces in good condition have sold for more than £500.
The football 50p is one of 29 designs minted for the 2012 Olympics - and you'll find several others in the top ten too. If you find one of these, you could be in for a windfall of up to £20.
Like the football 50p, the judo one is worth up to £20 - but only if it's in excellent condition.
The 2012 triathlon 50p piece is slightly less collectible than the football and judo coins, but is still worth quite a lot more than its face value. You can expect to get up to £16 if you're lucky enough to find one.
Next on the list is the 2012 Olympics wrestling coin, but this is rather less desirable than the others. You'll get up to £8 for one if you're lucky.
The 2012 Olympics tennis coin is a little less desirable, but could still be worth around £5 to a collector.
On its own, the 2012 Olympics goalball 50p is worth around a fiver. If it's sold as part of a 2012 Olympics collection, though, it could be worth as much as £20.
8. Jemima Puddle-Duck
Issued to celebrate what would have been Beatrix's Potter's 150th birthday, this is one of none deswigns featuring her characters. This particular one is the rarest, typically selling for between £5 and £8.
Towards the bottom of the top ten, 50p pieces aren't necessarily worth much more than thewir face value. There's a 2012 rowing coin up for sale on eBay right now, for example, with a price tag of just £1.50.
This coin, too, isn't worth much more than its face value unless it's in perfect condition or being sold as part of a set. Expect to make £1 to £3.
Incredibly valuable coins
Incredibly valuable coins
This Australian coin was the first half crown minted under Edward VII. The price for a Melbourne coin in good condition is particularly high because around half of them were produced with faults. It’s now worth £7,500 and has risen in value some 13,789% since it was first in production
The only half crown on the list gets its position from its rarity value. However, the fact this is a silver coin rather than a gold one does affect its value - so it’s worth £10,500. It’s significantly less than others on the list - but it has still appreciated 79,445%.
This is the newest coin in the top ten, and the first year that sovereigns were produced featuring the Queen. The coin was produced in small numbers for investors - rather than for circulation - so is thought to be worth £12,500, due to its rarity.
This is another collectable gold coin prized for its rarity value. It’s worth £15,000 today and has appreciated 191,716%
This was issued in very small numbers, as it was produced during WWI. As a result, few are available - especially as uncirculated coins - so one in good condition will fetch £16,000.
This is another coin prized for its rarity, thanks to a relatively low number being minted, and more being taken out of circulation during WWI. It’s now thought to be worth £17,000 after appreciation of 42,084%.
This 1926 coin has shot up in value and is now worth £31,500. The rise in value is partly to do with a very low mintage, and partly to do with the fact that people were asked to hand their sovereigns over to be melted down during WWI, which took many of them out of circulation.
This brass threepence from 1937 has benefited enormously from the fact that Edward didn’t stick around for long to get too many coins struck in his image before he abdicated. It is now worth £45,000.
This 1933 penny has seen a stunning appreciation in value and is valued at a whopping £72,000 today. The value is due entirely to rarity. Only around seven British versions of this coin were minted, and were intended for the King to bury under the foundation stones of new buildings. They have been subject to theft, and a few are said to be in private hands now.
This isn’t the oldest coin in the list, but it was produced in a year when all gold coins were recalled and exchanged for paper money - so the vast majority were melted down. Its rarity and popularity puts it head and shoulders above the rest. It is worth an eye-watering £6,500,000, and has increased in value 2,178,885% since it was produced.