French crown jewel diamond brooch sold for pounds 1.4m.
It was commissioned by Napoleon III for the Empress Eugenie and created by the Parisian jeweller Kramer in 1855.
The massive brooch was worn by the empress as the central part of a girdle round her waist and designed to match similar brooches on her shoulders.
But the French crown jewels were split up and sold by order of the Republican government in 1887 and the brooch was brought by Mrs William Astor, a leading American socialite.
It remained in the family until the early 1990s and was the highlight of a jewellery auction which took just over pounds 4 million at Sotheby's.
A 17th century coin found by a woman planting potatoes in her back garden was sold for pounds 4,400 at auction today.
The Massachusetts two penny piece from 1662, found in south Devon, was bought by a US collector who flew over for the auction at Dix, Noonan and Webb in St James's, central London.
Chris Webb, the auctioneer, said after the sale: 'When this lady found the coin it just looked like a washer, but she rinsed the mud off and sent it to us with a splendid result.
'She did not attempt to clean it which would have reduced the value by half. It was in very fine condition and an early American rarity.'
The tiny coin was decorated with an oak tree and dated from 1662. The unnamed vendor lives at Christow, near Exeter.
An ancient track running near her back garden leads to an old Quaker burial ground which may explain the coin's presence in south Devon.