We are all being urged to check our wallets and down the back of our sofas after a 50p coin sold for more than 300 times its value at auction this week.

The 50p coin in question was released in 2009 to mark 250 years since the opening of Kew Gardens in 1759.

Just over 200,000 copies of the coin were produced by The Royal Mint, which lists the anniversary Kew Gardens coin as its most valuable.

The coin features the Chinese Pagoda at the Royal Botanic Gardens on the tails side and a portrait of the Queen.

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After being listed on online auction site eBay, the 50p coin attracted 20 bids before selling for £158 on Sunday.

What makes a coin valuable?

The 50 pence piece has become the most valued and collected coin in the UK, with many collectable designs appearing on its heptagonal canvas.

Its 27.5mm diameter makes it the largest of any British coin, and allows space for decorative pictures. It has often been used to celebrate big events over the past 50 years of British history.

The rarest coins tend to be of the greatest value, with the mintage (number of coins with each design made) being the fundamental attraction for collectors.

Along with the design, other aspects of the coin which increase value are the condition of the coin and whether it has an error in its design.

The way in which it is sold can also determine the coin’s value - while some coin collectors will bid vast amounts of money on ebay or at auction, others opt for more robust valuations by selling via a coin dealer.

Rarest 50p coins in circulation the UK?

The Royal Mint has revealed the most valuable 50p coins in its collection.

The rarest is the Kew’s Garden 50p, which was designed to mark the 250th anniversary of the gardens in 2009. Only 210,000 coins were ever minted with this design.

The Kew Gardens 50p sells for £156.25 on average, but one seller received over £700 for one when they sold it on eBay.

The other rarest coins stem predominantly from the 2011 Olympics, with the wrestling, football and judo coins among the most valuable. Only 1.1million of each of these coins were produced.

Flopsy bunny and Peter Rabbit designs which were produced in 2018 are also highly valuable.

These coins - 1.4 million of which were minted - depict the characters from Beatrix Potter’s novels and celebrate the life of the English writer and these sell for around £5.

In 2019, 500 million coins were produced, with three new 50p designs.

These included one of Arthur Conan Doyle’s Sherlock Holmes, Paddington Bear at St Paul's Cathedral and the Tower of London.

Top 10 most valuable 50p coins, according to Royal Mint

Here is a list of the top 10 most valuable coins, when they were made and how many were minted:

  1. Kew Gardens (2009), 210,000
  2. Olympic Wrestling (2011), 1,129,500
  3. Olympic Football (2011), 1,161,500
  4. Olympic Judo (2011), 1,161,500
  5. Olympic Triathlon (2011), 1,163,500
  6. Peter Rabbit (2018), 1,400,000
  7. Flopsy Bunny (2018), 1,400,000
  8. Olympic Tennis (2011), 1,454,000
  9. Olympic Goalball (2011), 1,615,500
  10. Olympic Shooting (2011), 1,656,500