A silver Kew Gardens 50p coin sold for a whopping £400 at the Royal Mint's first ever London historic coin auction last month.
It surprised auctioneers and numismatists nationwide by going for 10 times its estimated sale price of £40.
Sovereign Rarities, a coin dealer that managed the auction, said that only 7,500 of the special edition collectors coins were made.
Find out how much other rare coins sold for at auction and whether you could have a valuable coin sitting at home.
A rare gold Kew Gardens 50p coin also sold for well above its estimated sale price.
Originally pegged to sell for £400 to £600, the collectors' coin went for an incredible £2,000. According to Sovereign Rarities, only 1,000 of the gold Kew Gardens 50p coins were made, making it a rare collectors' edition.
Similarly to the silver design, the gold Kew Gardens 50p coin was a proof coin, meaning that it was not released into general circulation.
For every new coin design created, the Royal Mint usually makes a batch of proof coins, especially for collectors. These coins are not circulated and are often made from different metals to circulated coins.
The Kew Gardens 50p coins were designed by Christopher Le Brun to celebrate the 250th anniversary of London's Kew Gardens and in 2009. Only 210,000 were minted and went into general circulation.
The Kew Gardens 50p coins were among 600 lots of coins and medals up for auction.
Other stand out sales included a historic William III with an Elephant and Castle mint mark coin, which sold for £155,000 after being estimated to fetch somewhere between £35,000-£45,000.
The table below shows some of the highest selling items during the auction:
|Coin||Sale price||Estimated sale price|
|William III Five Guinea||£155,000||£35,000-£45,000|
|Charles II Five Guinea||£130,000||£35,000-£45,000|
|Victoria Five pound Una & Lion||£120,000||£120,000-£150,000|
|Kew Gardens Gold 50p||£2,000||£400-£500|
|Kew Gardens Silver 50p||£400||£40|
The value of a coin is a difficult attribute to quantify as it lies very much in the eyes of the coin collector. The following factors, however, can give you an indication of what you might be able to sell your coin for.
The mintage of a coin indicates how many of a particular design were created and released into circulation.
Generally speaking, the lower the mintage figure, the less likely it is for that coin to pop up in your spare change, making it harder for collectors to find.
This means that collectors are more likely to pay a higher sum for that particular coin to complete their set.
Older coins can often be seen as more valuable as they can be more difficult to collect.
This is because they can become worn, damaged or lost over time.
Resources such as Change Checker's Scarcity Index can help give an indication of what a coin's value could be.Change Checker is an online platform that allows you to trade rare coins and notes with other collectors.
The Scarcity Index takes into account:
Coins are given a score out of 100 and the higher the score, the rare and potentially more valuable a coin is.
There are now over 35 different 50p coin designs in circulation in the UK and the 2009 Kew Gardens 50p coin is the rarest and most valuable of all. Only 210,000 were minted.
The 2016 Jemima Puddle-Duck is currently the third rarest 50p coin in circulation and only 2.1m were minted.
You can see the full list of rare 50p coins in the graph below.
If you think you've stumbled across a rare coin, the first thing to do is get in touch with the Royal Mint to make sure that it's real.
They'll often send you a letter to confirm your coins' authenticity.
Once you have confirmation that your coin is legitimate, you'll be able to sell it online or via a coin dealer.