This fascinating link gives more details about the history of the necklace between Archduchess Sophie and Harry Winston, as well as about its gemmological characteristics:
"Napoléon Bonaparte presented this magnificent necklace to his second wife, Marie-Louise, Empress of France, as a gift to celebrate the birth of their son, the emperor of Rome, in 1811. The necklace was designed and assembled by the jewelry firm Nitot and Sons of Paris and complete in June 1811 for the fee of 376,274 French francs. Following the fall of Napoléon and his exile to Saint Helena in 1815, Marie-Louise returned to her Hapsburg family in Vienna, Austria, with her personal jewels, including the diamond necklace. After her death, the necklace passed to her cousin, Archduchess Sophie, her sister-in-law, who removed two diamonds from the necklace in order to shorten it and put them into earrings, the current whereabouts of which are unknown. Following the Archduchess’s death in 1872, the necklace was inherited by her three surviving sons, one of whom, Charles Louis, later acquired the interests of his two brothers. Charles Louis’s third wife, Maria Theresa, inherited the Napoléon necklace upon his death in 1914.
In 1929, Archduchess Maria Theresa sent the jewel to the United States to be sold. But the agents she chose to sell the necklace were not the persons they claimed to be, i.e. "Colonel Townsend," who had allegedly served in the British Secret Service, and "Princess Baronti," a novelist. In fact, the Townsends' true identities have never been confirmed. The necklace arrived in American at about the same time as the stock market crash, and the Townsends quickly realized that they never would be able to sell the necklace for the $450,000 asking price. The couple engaged Archduke Leopold, Marie-Theresa’s grand-nephew, who was from the ruined branch of the Hapsburg family and who worked in New York as a "sausage sailor man", in order to authenticate the necklace to prospective buyers. The Townsends negotiated deals to sell the necklace several times, and eventually sold it for $60,000 to David Michel, a New York diamond dealer. The Townsends sent $7,270 to Maria Theresa and kept the balance to cover their "expenses related to the sale," which included a reported $20,000 for Archduke Leopold. The affair ultimately went to court, as Maria Theresa had engaged an emissary to retrieve the diamonds and had revoked the Townsends’ authority to sell the necklace. The necklace was returned to Maria Theresa, Archduke Leopold went to jail, and the Townsends took flight and were never seen again.
In 1948 the necklace was sold by the Hapsburg family to French dealer Paul Weiller, then to the New York diamond dealer Harry Winston and finally to Mrs. Marjorie Merriweather Post. In 1962, she gave the necklace, in its original case to the Smithsonian Institution."
on August 24, 2015, 3:51 pm, in reply to "