A rare Indian necklace featuring some of the world's oldest and largest diamonds is going on sale with an asking price of 20 million US dollars.
The 17th century Mughal Golconda mirror diamond necklace features five pendants each made up of a table-cut diamond and an emerald in a gold setting.
Suspended from a gold and cream woven cord, the jewellery boasts the largest-known matching set of flat diamonds from Mughal India and is going on private sale at Bonham's in London.
Matthew Girling, chief executive of Bonham's for UK and Europe, said the piece was far more than just a necklace.
"It is an extraordinary collection of five diamonds - more than just a necklace - that were cut in the 17th century so they are some of the earliest faceted diamonds.
"They were probably once part of a much larger piece of jewellery that has changed at some point.
"It is now five diamonds with five emeralds in a gold setting which was done in the late 18th or 19th century when a lot of Indian gems were taken out of jewellery and remodelled in a more European way."
The 28.00 carat table-cut diamond in the central pendant is the biggest on record, Mr Girling said.
"As far as records go there are no table cut diamonds in existence bigger than the one in the middle of this necklace, so records show this is the largest table cut diamond known to survive."
Mr Girling added that a necklace of such beauty and rarity would be a worthy addition to a museum.
"It is museum quality without a doubt and I would be surprised if it ever gets worn again," he said.
"It would be nice if it could be seen by many people so it would be a wonderful if a museum were to buy it."
The current owner of the necklace remains a mystery, and Mr Girling would only reveal it was an individual gentleman.
"The owner wishes to remain anonymous but he is a connoisseur and collector of gem stones," he said.
Another impressive and historic diamond is due to go on display in London tomorrow.
The 34.98 carat Beau Sancy, which was worn by Marie de Medici at her coronation as Queen Consort of Henri IV in 1610, was passed through the royal families of England, France, Prussia and the House of Orange over 400 years.
The modified pear double rose cut diamond will be displayed at Sotheby's in London tomorrow and from April 29 to May 1 before it goes on auction at Sotheby's in Geneva.
It is estimated to fetch between £1.2 million and £2.5 million.