Commemorative coins to celebrate an anniversary, event or figure of historical importance may be of interest to collectors.

For those looking to get minted, these collectors tend to look out for those coins with rarity value. This could be because a small number are in circulation or because they’ve been minted with ‘mis-strikes’, according to Which?. This is where an error is made in the minting process that gives the coin irregularities, such as a missing date or a misspelling.

According to the Royal Mint, the Kew Gardens 50p is officially the rarest coin in circulation, as only 210,000 were made. For reference, there are currently three billion normal 50p coins in circulation.

Other valuable 50p coins

Which? along with Changechecker have come up with three other recently minted 50p coins that look set to be classics.

It uses a ‘scarcity’ index with 100 being the most scarce, along with an approximate value, based on the median ‘sold’ listing for each coin on eBay. However, many of these coins have been selling for 100% more than the average:

How to get the best price for your coins

The value of your coins depends entirely on how much a buyer is willing to pay. The only certain value is the one on the coin.

Here’s the Which? guide on working out a fair price for your coins:

• For an estimate, try sites such as the Westminster Collection. Several of the coins we saw listed for thousands of pounds on Ebay were available there for under £10.
• Changechecker.org’s scarcity index takes into account mintage figures, demand and how easy it is to find. If a coin has a high scarcity index, it’ll probably have a high coin collection appraisal value.
• Look at the minting stats on royalmint.com/discover to see how many were originally in circulation. If it’s less than a few million, your coin’s likely to fetch more than its stated value.
• While you can swap your coins on sites such as Changechecker, it’s best to sell on auction sites such as eBay. However, items listed on these sites can give misleading impressions. A 2015 Battle of Britain 50p listed for £2,500, even though this coin’s mintage was 5,900,000 – far more than any of the Olympic 50ps in circulation.
• Searching the full name of the coin on eBay and clicking ‘sold listings’ will show you how much others have sold for. But take the highest sold listings with a pinch of salt – not every ‘sold’ auction results in a proper sale.