Thomas Earnshaw Pocket-Chronometer Movement Signed Robert Tomlin
Record status
Individual type · partial
Period
1778-1788 (circa 1783)
This pocket chronometer movement was constructed by Thomas Earnshaw circa 1783 and features a backplate signature reading 'Robert Tomlin Watch Maker to the King London No 1400'.
Created during the licensing arrangement linked to Thomas Wright's 1783 patent, it incorporates an early version of Earnshaw's spring detent escapement. The mechanism employs a full-plate brass frame with turned pillars, maintaining power, gilded gear work, and jewelled escapement pivots. The white enamel dial features black Roman hour numerals, Arabic five-minute calibrations, and an inset subsidiary seconds register at 6 o'clock.
Evidence at a glance
- Linked sources
- 1
- Photograph views
- 1
- Catalogue references
- 0
Counts describe this entry’s documentation, not authenticity, rarity or completeness. Photographs may show one specimen; check each caption and licence.
Technical characteristics
- Type
- Pocket watch movement
- Escapement
- Spring detent escapement
- Provenance
- Courtenay Adrian Ilbert Collection
- Dial Diameter
- 44.60 mm
- Movement Maker
- Thomas Earnshaw
- Place recorded
- United Kingdom
- Backplate Signature
- Robert Tomlin Watch Maker to the King London No 1400
- Maker / attribution
- Thomas Earnshaw
Design
- Visible features
- • Flat white enamel dial with Roman hour numerals and outer Arabic five-minute chapter ring • Subsidiary seconds track positioned at 6 o'clock with no seconds hand fitted • Visible hairline cracks extending through the upper right sector and edge chipping near the 20-minute mark • Centrally mounted hour and minute hands, with the minute hand displaying an ornate piercing
- Dial and Condition
- The flat white enamel dial features Roman hour numerals and Arabic five-minute numerals. The minute hand is recorded as not original and poorly repaired; the seconds hand is missing from its subsidiary track. The balance and spring exhibit signs of deterioration. The spring is pinned to an overhanging stud, and as it projects through the stud for a quarter of a turn, the museum catalogue suggests it may not be original. The detent is described as deteriorated, and the steel banking pin displays signs of rust.
- Movement Construction
- The movement features a full-plate construction with turned pillars, lacking a barrel bridge, and possesses an unusual pierced and engraved balance bridge. The fusee includes maintaining power with a brass ratchet wheel, and the setting-up work is located under the barrel, described as an unusual feature in a chronometer. The escapement is an early form of Thomas Earnshaw's design. Adjustments are provided by three screws on the back plate, which control the detent position, height, and spring tension, respectively.
- Historical Context and Production
- This pocket chronometer movement was constructed by Thomas Earnshaw, dating to approximately 1783. The movement is linked to a patent agreement (No. 1354) taken out by Thomas Wright in May 1783, under which Earnshaw produced movements for other watchmakers to recover patent costs. The back plate is signed 'Robert Tomlin Watch Maker to the King London No 1400'. It is noted as one of two known examples produced under this specific agreement to bear the required stamp, the other being signed 'Jessop Southampton' (No. 19, in the Time Museum, Rockford U.S.A.).
Identification
- Reference
- 1958,1201.1752
- Serial number
- 1400
- Source note
- Facts transcribed from the linked source listing or collection record. Attribution and specifications are source-reported and have not been independently authenticated.
Catalogue references
No catalogue numbers recorded. Numbers are only published once transcribed from a verified edition of a standard catalogue — they are never inferred.
Research required
- Research required: The museum catalogue notes that the minute hand is not original and has been poorly repaired, while the seconds hand is missing.
- Research required: Only the dial side of the movement is visible in the photograph.