Important Modern & Vintage Timepieces

Geneva, Nov 13, 2016

LOT 450

THOMAS EARNSHAW POCKET CHRONOMETER WITH Z BALANCE SILVER "Pocket Chronometer with "Z" balance" Thomas Earnshaw, Invenit et Fecit, No. 486 of the sort/2827. Very fine and rare, silver pair-cased pocket Chronometer with Earnshaw's spring detent escapement and Earnshaw's "Z" compensation balance

CHF 3,000 - 6,000

HKD 24,000 - 48,000 / USD 3,000 - 6,000

Sold: CHF 7,250

OUTER: two-body, polished. INNER: two-body, "bassine", polished. White enamel, radial Roman numerals, outer minute track, subsidiary seconds. Gold "heart and poker" hands. 42 mm. secured by screws, gilt full-plate with cylindrical pillars, fusee and chain with Harrison's maintaining power, Earnshaw spring detent escapement, escape wheel jeweled with endstones in screwed chatons, Earnshaw's "Z" bimetallic compensation balance with sliding timing weights and two steel mean time screws, single-footed clock with endstone in screwed chaton, free-sprung blued steel helical balance-spring.

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Grading System
Grade: AA

Very good

Case: 3-8


Slightly scratched

Movement: 3-6*


Slightly oxidized

Overhaul recommended, at buyer's expense

Dial: 3-73-01


ENAMEL AND VARIOUS TYPES OF DECORATION Chipped under bezel,not visible when closed

HANDS Original


Dial and movement signed and numbered. DIAM. 61 mm. THICKNESS 27 mm. Using Earnshaw's numbering system, the first number is the number of watches made at that point using Earnshaw's spring detent escapement. The second number, in this case 2660, is the total number of watches produced at that point. THOMAS EARNSHAW (1749-1829) Born in Ashton-Under-Lyne in Lancashire, by 1780 he had the reputation of being a very fine watch finisher. He invented the modern Chronometer spring detent escapement towards the end of 1780, a design that he insisted was stolen by Arnold. However, it is likely that Earnshaw and Arnold arrived at their conclusions separately. Earnshaw perfected the fusing together of brass and steel to make laminae for compensation balances which previously had to be riveted.