Because they come across as peculiar, bidding wars can break out as collections scramble to claim something unique for their own.
But from one day to the next, interest can change on particular rare coins.
The Kew Gardens 50p remains at the top of the charts on Change Checker’s scarcity index so often collections are just after a copy because of the rare design.
There’s no hard and fast guarantee you’ll be minted snapping one up, though others have had success in the past, and a faulty one could boost your chances too.
Could one crop up in my change?
The Royal Mint manufactures between three million and four million coins a day, so mistakes will often happen and can rock up in your change.
Error coins are still legal tender too, so one could easily fall into your possession through any kind of transaction.
If you spot a coin that looks different to normal or is imperfect, you can check it against other listings on eBay to see how much others are selling for, or are willing to pay for a similar strike.
But remember that on eBay, a buyer can always pull out of the sale, which means it won’t have sold for the price that it may say it has.
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Experts also warn of fakes – especially when it comes to buying and selling on eBay – so you have to be careful when you’re on the hunt.
Change experts like Coin Hunter or Change Checker will help you verify if it’s real too, and they can help place a value on the coin that might put some weight in your wallet.