So called from Nicholas de Harlay, Sieur de Sancy, who bought it for 70,000 francs (25,000. Louis XV. wore it at his coronation, but during the Revolution it was again sold. Napoleon in his high and palmy days bought it, but it was sold in 1835 to Prince Paul Demidoff for 80,000. The prince sold it in 1830 to M. Levrat, administrator of the Mining Society, who was to pay for it in four instalments; but his failing to fulfil his engagement became, in 1832, the subject of a lawsuit, which was given in favour of the prince. We next hear of it in Bombay; and in 1867 it was transmitted to England by the firm of Forbes & Co. It now belongs to the Czar.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894