John Arnold & Son, London

• Movement: gilded full plate movement, spring detent escapement, slot and shaped foot finishing adjacent to winding square shroud, jewelled to the fusee, ‘OZ’ compensated
balance, gold helical spring, decoratively engraved balance cock with blued steel stud arm, diamond endstone • movement signed John Arnold & Son, London, No. 99 Inv.t et Fecit
• Dial: white enamel dial, Roman numerals, outer minute ring, large subsidiary seconds, blued steel hands, signed and numbered 99
• Case: plain silver consular case with London hallmarks for 1786 and maker’s mark IL in cameo for John Laithwait

Plaut Collection

Terence Camerer Cuss, The English Watch 1585-1970, 2009, p. 291, pl. 179

Hans Staeger, 100 Years of Precision Timekeepers from John Arnold to Arnold & Frodsham 1763-1862, 1997, pp. 171-172 & 183, colour illustrations p. 184 

Movement is running at time of cataloguing, however it is intermittently stopping and re-starting. Dial appears to be in good condition. Case in good overall condition for the age, very minor and small depression towards base of 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."

On 2nd May, 1782, John Arnold applied for a patent for a new form of escapement and balance. The patent, no. 1328, pertained to Arnold’s new spring detent escapement. The spring detent escapement provided many advantages over the pivoted detent, notably, the latter had relied on a powerful mainspring and necessitated oiling of the pivots and the point at which the return spring rubbed against the locking arm. Over time the strength of the mainspring caused unnecessary frictional wear, whilst the changing condition of the oil altered the friction. Vaudrey Mercer notes in his book, John Arnold & Son, that the earliest known and unaltered spring detent escapement by Arnold is no. 75 which Mercer dates to 1781. The present watch, no. 99, is hallmarked for 1786 and is signed by Arnold in conjunction with his son. Only a handful of large sized Arnold & Son chronometers have survived and this watch, no. 99, is in exceptional condition. Patent 1328 also covered the balance types he had employed since 1778, i.e. the double T and double S types as well as his newest form, the ‘OZ’ (see Vaudrey Mercer p. 60). The watch is fitted with an ‘OZ’ balance and a gold helical spring. Arnold began fitting gold helical springs some time before 1784. On 6th March 1784, Arnold wrote to the Board of Longitude: “I have made (after a great number of experiments) gold helical springs which are not liable to be affected by moisture or taking up fresh phlogiston from the human body.” The springs were not pure gold but made from an alloy of 1/8 – ¼ copper to gold, see Vaudrey Mercer, John Arnold & Son, 1972, p. 67.

For a note on Arnold see lot 38, for a note on the ‘OZ’ balance
see lot 45.