A TINY mistake on your usual 20p coin could make it a whopping 350 times more valuable.
You will need to look out for one small detail if you want to mint some extra cash.

20p twenty pence obverse heads over 2012 coin[/caption]
The 20p coin that sold for a whopping £70[/caption]
Coins become more valuable if they have a low mintage, meaning not many of them have been created.
That means they’ll be harder to find – but they can earn you more money if you do spot one.
And not all coins need to be shiny and new to sell for a profit.
They can also be worth more if they have an error in the design, such as if they’re missing a small detail.
Something similar happened to one lucky person who sold their regular-looking 20p coin for a whopping £70 at the RWB Auction’s February 2025 sale.
What makes the coin so unique and worth appraisal is that no one knows how old the coin is.
That is because the coin had no date on it – making it incredibly rare.
Such mistakes can happen from time to time and go unnoticed, meaning there is a chance you may have a super rare coin hiding in the change – all you need to do is look for mistakes.
Meanwhile, one of the most popular types of coins to collect is are 50p piece.
This is because of their large surface area, as there is enough space to add new and intricate designs.
A 2019 Kew Gardens 50p went under the hammer on eBay for a whopping £122.09 – 244 times its face value.
The coin, which attracted 13 bids, is one of the most sought-after pieces among coin collectors.
The Royal Mint, the official maker of British coins, regularly puts limited edition pieces into general circulation.
In some cases, extremely rare 50p pieces have sold for a whopping £950.
Errors make a coin unique, which means they will most likely be worth more, as there a fewer of them.
Even without a misprint, if a coin has a low mintage, there are fewer of them in circulation and so are deemed rare.
As a general rule of thumb, the rarer the coin, the more valuable they are to collectors.
How to sell a rare coin
If you have managed to get your hands on a rare coin, there are a few ways you can go about selling it.
Online platforms like eBay, Facebook marketplace, or trading apps can be easy to use – but there are risks.
Scammers may try and target sellers with this trick – they’ll say they are keen to purchase the item and ask for money upfront for a courier.
They have no plan on collecting the item and are only using the courier to grab free cash.
When buying or selling on Facebook Marketplace it’s advisable to meet up in person – make sure this is a safe space and avoid payment links.
Many sellers will choose to handle cash when meeting to limit the risk of scams.
To ensure the ultimate safety you can sell rare coins at an auction.
This can be done through The Royal Mint’s Collectors Service which has a team of experts who can help you authenticate and value your coin.
Finally, you can sell rare coins on eBay.
What are the most rare and valuable coins?
- Five rarest coins – do you have one?
- The 13 most valuable £2 coins in circulation
- How valuable are the rarest £1 coins?
- Most rare and valuable 50p coins in circulation
- Rare and most valuable 20p coins that could be worth up to £750
- Rarest 10p coins in circulation
- Rare 2p coins revealed
- How to check if you have a rare and valuable banknote