It was a ring fit for a princess – and now it is on sale in Birmingham for a cool £750,000.
The stunning five-carat diamond piece was made for Princess Margaret in 1970 and is among the most expensive single items ever sold at the Antiques for Everyone fair.
The four-day show, being held at the NEC, will also see more than a dozen of her other belongings sold off – including a bed from Glamis Castle in Scotland in which she was believed to have been born.
There is also a Cartier watch bought for her as a Christmas present by the Queen Mother, valued at £175,000, and a solid gold clock.
Each of the items was authenticated by Margaret’s son Lord Linley.
A spokesman for sale organiser Riverside Antiques said: “The collection is part of her fascinating, and sometimes turbulent, life. Many of these items were personally used or worn by her.
“They would almost certainly have been valuable sentimentally to her.
“But, like any good home, things from time to time get sold off.
“This is a once-in-a-lifetime opportunity to buy a piece of history as an investment for the next generation.
“As well as the pricier items, there are also ones that start at around £3,000.
“There are enamel boxes, and mother of pearl card cases which were small personal items of the Princess’s and were kept in her private apartment.
“We were unable to bring the bed here for obvious reasons, but we have photographs available of it.
“We acquired these items through our contacts within the industry and each one comes with a certificate and a leather-bound piece with Princess Margaret’s crest.”
The Antiques for Everyone fair runs from April 4 to 7.
It will also showcase one of the world’s finest collections of mechanical propelling pencils.
The KB Collection, now owned by Bond Street dealer Kenneth Bull, dates from the Victorian era and features 600 unique pieces.
BBC Antiques Roadshow expert Judith Miller said: “Some of the pieces are very rare and quirky.
“Each contains an ingenious telescopic mechanism that’s an engineering masterpiece in its own right and would often take weeks to make.”
Two of the pencils, one called Nelson’s column and a Cartier gold and enamel version, are worth around £10,000 and £15,000 each, respectively.
But many of the more common pencils start from around £100.