English chronometer with spring detent escapement Circa 1840

Gold open faced watch by Thomas Earnshaw “Junior”
–
A very fine English pocket chronometer with spring detent escapement, circa 1840. In a later custom made case, circa 1937.
The polished case is 18 carat gold with engraved cartouche, gold dome, case maker’s punch mark “JTW” and London hallmark 1937. The dial is enamel with radial Roman hours, auxiliary seconds and gold spade hands. And the full plate movement is keywind, frosted, gilt and signed, with chain/fusee, Harrison’s maintaining power device, moulded movement pillars, screw compensation balance, freesprung blued helical balance spring with both sides passing terminal curves, florally engraved balance cock and chatoned diamond endstone on balance.
–
Diameter: 55 mm
–
Weight: 152 g
–
Signed: Thomas Earnshaw, London
–
Thomas Earnshaw “Junior”
Earnshaw was the father of the modern mechanical chronometer. If not its inventor, he combined the best features of the system, invented his own spring detent escapement which became the standard inthe vast majority of pocket and marine chronometers since. Earnshaw system was patented in 1783. Earnshaw did not have money to pay for the patent fees. His master, Thomas Wright, paid the fees in exchange for royalties.