The rarest 50p coins have been revealed - and some are worth hundreds of pounds.

Coin site ChangeChecker has a list of the coins to watch out for and if you find any of the ones below in your pocket you could be quids in.

The value of the coin depends on the demand from collectors.

In general, the lower the mintage the rarer the coin, and the rarer the coin the more valuable it is.

That said, ChangeChecker's scarcity index is based on how many of each design are listed as “collected” by users and the number of times they have been requested as a swap.

The Argus: Some 50p coins can be worth hundreds of poundsSome 50p coins can be worth hundreds of pounds

The coins have all been circulated, so it’s possible you could find one in your spare change.

The Judo 50p is the most sought after, sitting just below the Kew Gardens 50p.

Both have been sold for hundreds of pounds on eBay in recent months.

In the most recent index, the Pentathlon 50p has climbed 10 spots and the Taekwondo 50p has dropped 10 places. 

The Sir Arthur Conan Doyle (Sherlock) 50p and the 2019 Paddington coins have entered the index relatively low.

How much are other 50p coins worth?

Many coins can be worth much more when sold on eBay as part of a collection.

Although sometimes you'll get better individual prices if another collector needs your coin to complete their collection.

Other coins sought after by collectors include the Beatrix Potter 50p coins.

These tend to go for less than £10 each but, the original 2016 Peter Rabbit coin did once sell for up to £840 on the auction website.

Coins with mistakes tend to be among the highest values because of their extremely limited numbers.

A rare error coin from the 2012 Olympics set sold for £590 on eBay last year.

The Argus: The current 50p Scarcity IndexThe current 50p Scarcity Index

New coins that could be worth a mint too

The Royal Mint recently re-released sets of five of the rarest and most popular 50ps to celebrate half a decade of the coin.

The new coins are made with old designs including Kew Gardens, Girl Guides and Scouts, but are stamped with the 2009 date which could make them super valuable among collectors.

The £90 collectors' proof sets sold out but you can still get uncirculated sets for £45 directly from the Royal Mint.

What makes a coin more valuable?

Generally, collectors look at the mintage figures of a coin to assess its value.

Rather than just basing a coin's value on the rarity, Changechecker.org looks at two other key pieces of information.

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This includes how many of each coin are listed as "collected" by members of the site, which indicates the relative ease of finding a particular coin.

The experts also track the number of times a design has been requested as a swap over the previous three months, showing the current level of collector demand.

While the index doesn't necessarily correspond to value, it is an effective indicator.