The Royal Mint has released a new 50p coin this week to celebrate the 20th anniversary of the famous children's book monster, The Gruffalo.
Three new Royal Mint 50p coins featuring the illustrated beast are now available to buy online, though the designs sold out within a day of launch.
The coins are not being released into circulation, so the only way to get your hands on one is through the Royal Mint website.
Here, Which? explains where the Gruffalo coin is being sold and looks at the most valuable 50p coins in circulation.
The commemorative collection of coins includes a silver proof, a gold proof and uncirculated version of the Gruffalo design.
The Sterling silver proof coin, which is currently for sale for £65, captures in full colour the beast's unmistakable orange eyes, thick brown fur and odd purple prickles. Just 25,000 have been produced.
The gold proof coin, of which 600 were minted, is currently priced at £795.
The uncirculated 50p, meanwhile, is available for £10, but the Royal Mint has not put a limit on mintage.
|Coin title||The Gruffalou00ae2019 UK 50p Gold Proof Coin||The Gruffalou00ae2019 UK 50p Silver Proof Coin||The Gruffalou00ae2019 UK 50p Brilliant Uncirculated Coin|
|Alloy||916.7 Au - Red||925 Ag Sterling Silver||Cupro-Nickel|
Source: Royal Mint
At one stage on Tuesday morning, more than 40,000 people were queuing to access the website, and here at Which?, it took us more than two hours to reach the front.
However, treat eBay listings with caution. A collectible coin is only worth what another collector is willing to pay for it.
Some sellers will list coins at an inflated price, or bid on their own product, to make it seem more in demand than it is.
These new 50ps mark the 20th anniversary of the tale of The Gruffalo, which was published 20 years ago by Macmillan's Children Books and has sold more than 13.5 million copies worldwide.
Writtenby Julia Donaldson and illustrated by Axel Scheffler, the book tells the story of a mouse taking a walk in a European forest and convincing other animals - including the terrifying Gruffalo - it is a fearsome creature.
It was adapted into a 27-minute animated film that premiered on the BBC on Christmas Day 2009 and was later nominated for an Academy Award.
Newly-released 50p coins are often popular with collectors, especially those released into general circulation. But it's not always clear how many coins have been minted.
You can see the full list in our graph below.
Several factors can determine whether a coin is worth more than its face value.
The first is how many coins are in circulation. If the mintage of the coin is low, and they're more difficult to find, then collectors might be willing to shell out more cash.
The second factor which influences the value of a coin is whether the design is particularly sought-after or sentimental. The more beloved the theme, the more likely people are to hang on to the coin, removing it from circulation and making it more scarce.
Thirdly, the coins' condition and whether it's free from marks or scratches can also have a big impact on whether a collector is willing to pay more.
Whether you're a coin enthusiast or an experiencednumismatist, it's worth doing your research thoroughly before spending money on a 'collectible' coin. Last year, Which? took a look at the and the potential risks.
You can find out more in our video about investing in coins.