A historic diamond has finally been located after disappearing during the aftermath of World War I in the early 1900s. Charles I, Emperor of Austria-Hungary, believed his empire was ending at in 1918 as the war was ending. To prepare, he arranged for the Habsburg dynasty’s family jewels to be moved to safety in Switzerland. The star of the collection was the fabled 137-carat Florentine diamond, once owned by the Medici family. Its rare size, cut, and colour – crystal clear, with hues of yellow and green – made the diamond, from India, world famous. But after the first World...