Sun Tiara circa 1907 made by Cartier with a yellow diamond, white diamonds, platinum, yellow gold.  Alternate sapphire setting.  

Sun tiaras are recorded from the beginning of the nineteenth century. At the 1889 Paris Exposition the jeweler Vever exhibited a model containing a 54-carat diamond.
Cartier’s first sun tiaras date from 1904 and were delivered to J.P. Morgan in New York and the Countess of Suffolk in London. In Londons Cartier’s were still designing sun tiaras in the 1920s, some of which were set with a large cabochon sapphire or emerald at the center. The last one was ordered in 1926 by the daughter of Mrs Cavendish-Bentinck.