A diamond ring to be auctioned in July is set to make its owner a sparkling profit.
The ring was bought for £10 at a car boot sale at West Middlesex Hospital in Isleworth, west London, in the 1980s.
It's expected to fetch £350,000 at Sotheby's - and it's not the first item to turn small change into a small fortune...
The Chinese vase: £10 to £61,000
After paying £10 for a floral vase at a car boot sale, the Hampshire-based owner decided to sell it on eBay.
When bids soared to £10,000, he withdrew it - and sought professional help in identifying just what he'd bought.
The £10 pot was, in fact, a rare enamel "two quails" vase, thought to have been made at Beijing's Imperial Palace at least 220 years ago.
John Axford, Asian art expert at Woolley & Wallis auctioneers, confirmed the "excellent investment" bore the four-character mark of Qianlong - the sixth emperor of the Qing dynasty - and would have been made in the palace workshop between 1736 and 1795.
The firm sold the vase in Salisbury in November 2016, where it made £61,000, including buyer's premium. That was double its guide price of £30,000.
Bountiful Buddha: £4 to £9,500
It was only six inches tall, but the multi-armed figurine earned a pensioner in West Sussex almost five figures.
Bought for £4, the piece was in fact an 18th Century Sino-Tibetan Buddhist sculpture.
Auctioneer John Nicholson thought it might fetch up to £700 at the sale in December 2015.
It eventually fetched £9,500 - leaving the seller "stunned and close to tears".
At the time, she said: "I thought it was different, but I couldn't believe it would go for anything like that amount."
Collectable cartoon: £2 to £1,100
A £2 cartoon bought at a London car boot sale spent two years under a bed before its value was revealed.
The female buyer broke the frame in a house move, so left it under a mattress.
When she eventually recovered it, she researched the signature and found it was by celebrated satirist and artist HM Bateman.
The cartoon - called The Larynx Preservation Committee Fail To Detect The Slightest Suggestion of Throat Trouble, In A Man Who Has Chain-Smoked One Thousand Cigarettes - sold for £1,100 by Nicholson's in May 2016.
Its guide price was £500 to £800.
The plant pot vase: £1 to £32,450
The BBC's Antiques Roadshow has uncovered many forgotten masterpieces.
In 2008, a £1 car boot sale vase was found, in fact, to be from renowned French Art Nouveau designer Rene Lalique.
The 12.5cm (5in) glass vase, which had been used as a plant pot, was identified as a 1929 work called Feuilles Fougeres.
The anonymous buyer, who picked it up at a sale in Dumfries in southern Scotland, was about to throw it away when they took it to be valued.
After speaking to the programme's experts, the owner swiftly changed their mind. The vase sold at Christie's in London for £32,450.