Check down the sofa: The '£1' British coin that's now worth £100,000

Britons may wish to undertake a thorough search of the back of their settees.

An exceedingly rare 200-year-old coin has just been valued at £100,000 – and there may be more of them out there.

The gold sovereign, which was minted in 1819 and given a nominal value of £1, has been put up for sale at the fixed price by the Royal Mint.

It said the valuation reflected the fact there were only 3,574 of the George III coins ever minted, with only around 10 known to have survived. But others could still be in existence.

It added that this particular sovereign, minted in the same year Queen Victoria was born, had been sourced and verified by its historic coin experts.

It will be sold via ballot on 12 July and potential buyers must apply online before 28 June.

Nicola Howell, director of consumer business at the Royal Mint, said: "We know there are people in the UK and beyond who value such treasures.

"Making the coin available to purchase for a fixed price is an incredible opportunity for those who want to own a piece of history."

Before it is sold, the piece will go on display at the Royal Mint Experience visitor centre in Llantrisant, south Wales, from 10 June.