Thomas Earnshaw, London

• Movement: full plate, spring detent escapement, flat three-arm steel balance, spiral hairspring, sugar tongs bi-metallic compensation, fusee and chain, cylindrical pillars, signed and numbered T. Earnshaw, Invt. et Fecit, 662/3114
• Dial: white enamel, Roman numerals, outer minute ring, subsidiary seconds, gold hands, subsidiary seconds with Arabic numerals, signed and numbered Thomas Earnshaw, Invt. et Fecit, No. 662
• Cases: plain gilt metal cases, the inner with winding aperture to back, inner case with maker's mark TC with axe above incuse for Thomas Carpenter 
• Deck box: later three-tier mahogany box containing keys

Terence Camerer Cuss, The English Watch 1585-1970, 2009, p. 336, pl. 212

Movement running at time of cataloguing. Dial with light scratches to the surface. Gilding to case worn to the band and pendant. Outer case with some wear to gilding at the edges and centre of the case back.
"In response to your inquiry, we are pleased to provide you with a general report of the condition of the property described above. All dimensions in catalogue descriptions are approximate. Condition reports may not specify mechanical replacements or imperfections to the movement, case, dial, pendulum, separate base(s) or dome. Watches in water-resistant cases have been opened to examine movements but no warranties are made that the watches are currently water-resistant. Please note that we do not guarantee the authenticity of any individual component parts, such as wheels, hands, crowns, crystals, screws, bracelets and leather bands, since subsequent repairs and restoration work may have resulted in the replacement of original parts. Since we are not professional conservators or restorers, we urge you to consult with a restorer or conservator of your choice who will be better able to provide a detailed, professional report. Prospective buyers should inspect each lot to satisfy themselves as to condition and must understand that any statement made by Sotheby's is merely a subjective, qualified opinion. Prospective buyers should also refer to any Important Notices regarding this sale, which are printed in the Sale Catalogue. In particular, please note it is the purchaser's responsibility to comply with any applicable import and export matters, particularly in relation to lots incorporating materials from endangered species.NOTWITHSTANDING THIS REPORT OR ANY DISCUSSIONS CONCERNING A LOT, ALL LOTS ARE OFFERED AND SOLD AS IS" IN ACCORDANCE WITH THE CONDITIONS OF BUSINESS PRINTED IN THE SALE CATALOGUE."

**Please be advised that bands made of materials derived from endangered or otherwise protected species (i.e. alligator and crocodile) are not sold with the watches and are for display purposes only. We reserve the right to remove these bands prior to shipping."

Studying the numbering sequence prepared by Anthony Randall and published in his book, The Time Museum Catalogue of Chronometers, the present watch can be dated more or less exactly to 1803. Thomas Earnshaw claimed to have invented the spring detent escapement in 1781, after he discovered inherent issues with the oiled pivots of the pivoted detent escapement. Previously collaborating with Brockbanks for the construction of chronometers with the pivoted detent escapement, Earnshaw and Brockbanks had a disagreement and Earnshaw approached Thomas Wright with the designs of his new escapement. At the time, Thomas Wright was watchmaker to King George III and, as Earnshaw lacked funds to apply for the one hundred guinea patent for his invention, the pair entered an agreement whereby Wright would apply and pay for the patent in his name. Earnshaw would then make movements for any other watchmakers who ordered them, adding a one guinea fee payable to Wright to cover the patent cost. The patent, no. 1354, was filed in 1783. Earnshaw listed names of makers for whom watches were made under this agreement and these included: Barraud, Frodsham, Margetts and Vulliamy. For a discussion of Earnshaw’s patent see: Rupert T. Gould, The Marine Chronometer, Chapter VIII, pp. 189-193.

From around the mid-1790s, Earnshaw fitted his chronometers with plain steel balances, spiral springs and 'sugar tongs' bi-metallic compensation (although he also continued to use the combination of compensation balance and helical spring). The arms of the ‘sugar tongs’ embrace the outer coil of the spring, altering their shape and length, the curved ends moving closer together or further apart with changes in temperature, thus compensating for the effect caused by these changes on the balance and spring. The timekeeping may not have been so constant, but the balance was lighter and the pivots therefore less susceptible to damage. This set-up would also have made the watch easier to regulate as compared to chronometer balances with timing screws. Shortly before 1800, Earnshaw ceased gilding the plates and blueing the steel parts of many, although not all, of his movements.