Although Marjorie Merriweather Post purchased the majority of her historic jewelry herself, this tiara was a notable exception, as it was a gift from her husband Joseph E. Davies in 1937. The tiara has a royal provenance as it was in the possession of the royal house of Saxony
The tiara, called 'Anna', was left by Marjorie Merriweather Post to her daughter Eleanor Close Berkassy, seen in the picture above.

The individual movable flowers were arranged symmetrically and the diamond ornaments, like a kokoshnik, set vertically with internal spacing so that it becomes a very fresh and elegant composition.

She wears the diamond diadem along with the famous earrings of her mother Marjorie Merriweather Post, formerly owned by the French Queen Marie-Antoinette. Also noteworthy is the four-row pearl necklace with diamond claps made by Cartier, one of her mother’s favourite pieces.

Later, the tiara went to the National Museum of Natural History of the Smithsonian Institution.

Marjorie Merriweather Post and her daughter Eleanor Post Close were both passionate jewellery collectors and clients of the most important Parisian jewellers ­ the first being Cartier, but also Boucheron and Van Cleef & Arpels

Marjorie Merriweather Post's collection was exceptional:  in 1923, she commissioned from Cartier an Art Déco bracelet set with a 58 carat sapphire; in 1928, a diamond and emerald necklace from which hung 24 important polished stones in the manner of the jewels of the Indian Maharajas and wearable as brooch and stomacher.
Her opulent jewels made her one of the icons of the 1930's. As a modern woman, Marjorie also took an interest in historical pieces, some of which are today on view at the Hillwood Museum, founded after her death, and at the Natural History Museum in Washington D.C. 
The most exceptional pieces of this collection are perhaps two Fabergé eggs reminiscent of her years spent in Russia, and the diamond necklace gifted to the Empress Marie-Louise by Napoleon I for the birth of their son, the roi de Rome, as well as the tiara of Empress Marie-Louise of France - later reset by Van Cleef & Arpels with turquoises.

True to her mother's memory, Eleanor Post Close donated to the Smithsonian Institute, in 1964, the beautiful pair of pear-shaped diamond earrings by Cartier dating from 1928. These stones of great purity, the present of her mother, came from the collection of the Yusupov princes and are believed to have belonged to Queen Marie-Antoinette, seen above in the picture worn by Eleanor Post Close. 

Information about the tiara is from "Spectacular: Gems and Jewelry from the Merriweather Post Collection" Liana Paredes, Hillwood Estate, Museum & Gardens, 2017, pgs 169 - 170