This 76.45-carat diamond gets its name from Archduke Joseph August (1872-1962), a previous owner of the gem and a prince of the Hungarian line of the Hapsburg dynasty. The Archduke was a descendant of the Emperor Leopold II, son of Empress Maria Theresa who owned the famous Florentine Diamond, one of the most notable and unique diamonds in history and an heirloom of the Hapsburgs for many years. But whereas the Florentine was unusually large for an Indian diamond and light yellow in color, the Archduke Joseph is a colorless diamond; it possesses the most notable characteristic of the best Golconda diamonds, namely a high internal clarity. Thus it has obtained D-color certification. It is cut in a rectangular cushion shape, perhaps a style of cutting that is not entirely unfitting with its Indian origin.
During the so-called "Traitor Republic," due to his great popularity, Archduke Joseph was put under surveillance while remaining at Alcsut. In August of 1919 he succeeded in becoming the Regent of Hungary but was compelled to resign within two months because the Allied Forces would not allow a Hapsburg to hold a commanding position in Hungary. In late 1944 he emigrated to the United States and returned to Europe to live with his sister, Princess Margaret von Thurn und Taxis, and published several memoirs and historical studies. He died in 1962, not completely removed from politics, having become a member of the Upper House soon after its restoration.
It is thought that at some point he gave the diamond to his son, Joseph Francis (1895-1957). Minutes taken on June 1st, 1933 record that the diamond, at the time belonging to Archduke Joseph, was at the time deposited with the Hungarian General Credit Bank in the presence of a state counselor. Three years later the diamond was sold to a European banker who kept it in a safe deposit box in France during World War II, where it fortunately escaped the attention of the Nazis.