Signed on the dial and the back plate. DIAM. 64 mm. A superbly made watch which exemplifies JÜRGENSEN'S talent. This is the EIGHTH of his famous series of chronometers. The escapement is based on ARNOLD's design. The brass escape wheel has cycloidal impulse faces. The detent is mounted to a gilded brass arm, which has micrometric adjustment, allowing for precision adjustment of the locking stone. Many were later converted to the Earnshaw type, and it is rare to find one which has survived in original condition.John Arnold was the first to use gold balance springs, probably employing them as early as 1779. Both Jürgensen's teacher and future father-in-law, JACQUES FRÉDÉRIC HOURIET and BREGUET, experimented with gold balance springs, but it was URBAN JÜRGENSEN who perfected them and put them to effective use. This would explain the application of the gold balance spring, which Jürgensen used in his best chronometers destined to go to sea. On the occasion of the 1862 Universal Exhibition Messrs. Jürgensen wrote: "the balance spring of gold not only presents the inestimable advantage of not being damaged by rust, but also not being influenced by magnetism. This property appears to be the more important one, with reference to box chronometers (destined for the sea), as the application of iron for shipbuilding is becoming ever more extensive. That the rates of chronometers with golden springs are as good as those with springs of steel is, in our opinion, best proved by the reports of the rates of several chronometers which have been observed on land, in the observatory of the Danish Navy, at Copenhagen, and also on board Danish ships of war".In the same note the Astronomer Royal and Director of the Observatory at Altona was quoted: "A considerable number of chronometers has been executed in Mr. Jürgensen's establishment, which have all proved superiority in their construction. We particularly draw attention to the cylindrical balance springs which are made of gold, and with respect... to alloys, elasticity, and dimensions, are based upon the experience of a great many years".Jürgensen & Sonner was founded in 1773. Following the wishes of his father, Jürgen, who was the founder of the company, Urban Jürgensen trained as a watchmaker in Paris, London, Geneva and Le Locle. It was under his management that the company's pocket watches and precision timekeepers for navigation and astronomy achieved international fame and recognition. Danish KING FREDERICK VI, granted him a Royal Appointment to supply the Court with watches and the Admiralty with chronometers. Their conception, design, the superb manner in which the mechanism is executed, as well as the excellent quality of the steel, soon made Urban Jürgensen's watches highly coveted collector's items.Urban Jürgensen & Sonner Copenhagen continues to produce complicated, classically-styled watches, individually, or in very small series. Provenance: Dr. Crott & Schmelzer Auktion XIII, October 1979, Lot 150. This watch is illustrated in The Jurgensen Dynasty by John Knudsen p. 114.