The woman who owned it had no idea of its true value and had kept the Italian pottery plate on her kitchen wall in her cottage home for many years.
She only realised its importance when she invited an antiques expert to her home in Somerset to value some items.
Ancient relic: This 16th century Italian plate hung precariously on a wall behind a door on a flimsy piece of wire before an art expert suspected it might be worth a lot of money. It sold at auction yesterday for £567,000
He said it was lucky the plate had not been damaged by the door being slammed open against it.
Despite it having an inch long repaired crack at its base, Mr Bromell told the unidentified woman it was in excellent condition and could be worth £100,000.
But the plate, which depicts a scene called The Feast of Herod, sold for an incredible £567,000 pounds when it was auctioned yesterday.
The owner, who had inherited the item from a relative, was said to have been delighted with the price.
Mr Bromell described the find as a true 'Only Fools and Horses' moment, similar to when Del Boy found an old pocket watch that had been hidden in his garage for years and only for it to be worth millions.
Measuring 16 inches in diameter, the plate depicts the feast of Herod, following a print by German printmaker Sebald Beham in which the king and his wife are approached by Salome with the head of St John the Baptist. The scene also shows a town, a river with bathers and a boat party.
Art expert Richard Bromell suspected the plate might be valuable and later identified it as Italian Maiolica pottery dating to around 1540
‘It had been there for years. She had inherited it and grown up with it but did not attach a great deal of value to it.
‘It was on the wall behind a door which was always open so you could only see about two inches of it.
‘When the wind blows through a house it can open and shut doors so it is quite frightening to think what could have happened if the door had blown back on to the plate.
‘In the position it was in it is lucky nothing happened to it over the years.
‘This is undoubtedly the most important piece of pottery I have held in my 28 years experience in this industry and is one of the highest prices ever paid for a piece of Italian pottery.
‘It was quite dusty when we first looked at it but the condition it is in for something which is nearly 500 years old is superb. The quality of the drawing on the surface is splendid.’
Mr Bromell said when he first saw the plate he thought it was a 19th century copy which would be worth a couple of thousand pounds.
'Important piece of pottery': The plate depicts the feast of Herod in which St John the Baptist's head is presented on a plate
Prof Wilson inspected the plate and concluded it was made in the Italian walled city of Urbino around 1540.
Mr Bromell said: ‘I was a bit nervous when I was driving it to the museum. I was taking extra care to avoid any pot holes.’
When it came to auction, there was interest among bidders from across the UK, France, Italy, Spain, Germany, Portugal, Switzerland and the U.S.
Mr Bromell said: ‘I was expecting it to fetch over £100,000 but it certainly exceeded those expectations without question. It was a fantastic result for the client.’
The winning bid came from London jewellery dealers SJ Phillips Ltd.
Francis Norton, director of the company, said: ‘The plate is in wonderful condition and we really fancied it and were determined to get it.
‘We don't know what we'll do with it yet but we might put it on display.’