200 - Thomas Earnshaw - Invenit et Fecit No. 413

Thomas Earnshaw - Invenit et Fecit No. 413 An important, museum-quality, double-cased pocket chronometer "6th Sort" with a spring detent escapement by Thomas Earnshaw Movm. No. 413/2635, Dimensions 63 mm, circa 1798, Weight 184 g, Origin England, Accessories Case: Outer and inner case—silver, smooth, case maker’s punch mark “TC” beneath an axe. The inner case is secured to the movement by a screw located at the bottom edge of the case. Dial: Enamel, off-white. Movement: Brass full-plate movement, chain/fusee, spring detent escapement, bimetallic “Z” chronometer balance with 2 screws and 2 movable trapezoidal weights, blued free-sprung helical hairspring with both sides passing. In our 78th and 80th auctions, we sold two nearly identical pocket chronometers: Lot 654/78, numbered 434/2655; and Lot 52/80, numbered 429/2660. The latter sold for €22,000. In our 92nd auction in 2015, we offered a small marine chronometer with an almost identical movement and a diameter of 42 mm (Lot 61). This piece bore the number 334/2387 and sold for €51,900. Thomas Earnshaw (1749–1829) began his training in watchmaking in 1763 and, from 1780 onward, produced watches for Brockbanks. Around 1781, he invented the spring detent escapement in his workshop, a mechanism that would be used almost universally for more than 150 years. In 1794–95, Earnshaw took over William Hughes’s company in High Holborn. For his improvements to the escapement, Earnshaw is generally regarded as a pioneer in chronometer making. His company produced about 3,000 pocket watches and about 1,500 marine and pocket chronometers of the highest quality. Case: very good, slightly scuffed. Dial: very good. Movement: very good, in working order, cleaning recommended.