One of the few watches from the celebrated Ilbert collection which did not enter the British Museum. Sold by Sotheby's on 28 October 1963, lot 82, it was originally the property of the Duc of Lorraine and vas sold by auction with his collection, lot No. 42 of the Catalogue des effets précieux de feu son Altesse Royale le Duc Charles de Lorraine et de Bar le Duc, Gouverneur des Pays Bas, dont la vente se fera publiquement à Bruxelles et commencera le 21 Mai 1781, published in Wins, L' It vas on the basis of this watch that it was possible to establish that the business of Julien Le Roy was continuel by his son Pierre, and that the invention of the fusée renversée was due to Jean Baptiste Le Roy, the second son of Julien and a member of the Académie Royale des Sciences (see Ch. Allix and G. Brusa : Antiquarian Horology, June 1968). The invention is recorded in Mémoires de l' Académie Royale des Sciences for 1763. In addition to the upside-down fusee, the movement has Le Roy' adjustable mounting for the crown wheel, in this case the back pivot is on the inside of the contrate wheel arbour to avoid the usual off-set. As the narrowest portion of the fusee is closest to the great wheel, an unusual form of stopwork had to be fitted. French watches with agate cases are extremely rare. Apart from the interesting technical features of the watch, the decoration of the case shows some thought, as the agate has been choses so that the portion of the design left in high relief is of contrasting colour to the ground. Exhibited at the International Art Treasures Exhibition, 1962, Catalogue No. 403, p. 50. Described and illustrated by G. Brusa: L'Arts dell' Orologeria .... 1979 and 1982, fig. 540-541. An off-print of the article published in Antiquarian Horology in June 1968, is coming with the watch.