The bargain-hunter, who does not want to be identified, snapped up the 5ins tall Chinese vase at a car boot sale because it looked interesting.
He only suspected he had something special when he put the item on eBay and he was inundated with questions about it and the bidding rocketed to over £10,000.
The man, from the Hampshire area, withdrew the listing and took the oriental piece to auctioneers Woolley & Wallis in Salisbury, Wiltshire, where it has been valued at £30,000.
John Axford, head of the auction house’s Asian art department, identified the vase as Imperial Chinese enamel, thanks to his extensive records of the Imperial Collection in Beijing.
He revealed to the startled owner that it was actually a rare ‘two quails’ vase and is at least 220 years old.
The vase has the four character Qianlong mark – the sixth emperor of the Qing dynasty – and would have been made by Imperial command in the Beijing Palace workshop between 1736 and 1795.
The lucky vendor had spotted the antique on a stall at the end of the day.
The vase comes with a 3ins tall enamel base which has previously suffered damage.
Mr Axford said: “We are delighted to be offering this lot.
“In 2012 we sold a brush pot on behalf of a charity to whom the pot was donated and it sold for £360,000.
“This vase is another example of why it is important that members of the public can bring items to specialist auctioneers for information and an auction appraisal.
“The owner bought it at the end of the day at a car boot sale, where it had just sat on a stall.
“He thought it looked interesting and decided to offer it on eBay but within a very short space of time he had been inundated with questions and the bids had gone to £10,000.
“It was then he realised it was possibly something very special.”
The vase and the hexagonal base it is attached to measure less than eight inches and it is believed there is a matching vase in the British Museum.
The vase will be sold at Woolley & Wallis on November 15.