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The Encyclopedia of Horology

Marine chronometer · Two-day marine chronometer

Thomas Mercer Two-Day Marine Chronometer

Partially verified

This 20th-century marine chronometer by Thomas Mercer is mounted in a brass gimbal within a mahogany box. The circular silvered dial features black Arabic numerals, an upper subsidiary dial tracking state-of-wind up to 56 hours, and a lower subsidiary seconds dial marked with the number 28400. The dial is signed in script 'Thomas Mercer' at the center and marked 'THOMAS MERCER LTD ST ALBANS ENGLAND' along the outer lower periphery. The auction house reports that it houses a two-day chain-driven fusee movement with a compensated detent escapement and Harrison maintaining power, accompanied by a tipsy winding key stored in a corner bracket.

Overhead view of the Thomas Mercer marine chronometer in mahogany box with gimbal and winding key
Overhead view of the Thomas Mercer marine chronometer in mahogany box with gimbal and winding key — Hutchinson Scott Auctioneers. Rights pending — permission not yet requested. Original source

Catalogue identity

Source
www.liveauctioneers.com
Category
Marine chronometer · Two-day marine chronometer
Maker / attribution
Thomas Mercer
Reference
Not recorded
Catalogue / lot identifier
0738
Source-reported date
20th Century
Country
United Kingdom
Source-reported serial
28400

Source-reported attribution and specifications are not independent authentication. A listing does not establish present ownership, current display, availability or permission to reproduce.

Object description

Dial and Visual Identification

The timepiece features a circular silvered dial signed 'Thomas Mercer' in script at the center. The lower outer periphery is inscribed 'THOMAS MERCER LTD ST ALBANS ENGLAND'. While the source description cites Roman numerals, the visible dial displays black Arabic numerals for hour markings.

The dial layout includes two subsidiary registers: an upper dial calibrated for up to 56 hours of power reserve and a lower seconds dial. The seconds dial is marked with the number '28400'.

Evidence for this section
  • “the silvered brass circular dial having Roman numerals”
  • “Signed 'Thomas Mercer' across the center and inscribed '28400' on the lower subsidiary seconds dial”
  • “Signed 'THOMAS MERCER LTD ST ALBANS ENGLAND' at the bottom rim of the dial”

Construction and Housing

The chronometer is mounted in a brass gimbal within a mahogany box measuring 18.5 cm in width, which includes a glazed viewing window.

A tipsy winding key is stored in a corner bracket within the mahogany enclosure.

Evidence for this section
  • “The Mahogany case with glazed viewing window and brass gimble”
  • “Box is 18.5cm wide”
  • “having original tipsy winding key”

Mechanical Details

The auction source reports that the chronometer houses a two-day chain-driven fusee movement, a compensated detent escapement, and Harrison maintaining power.

Internal components are not visible in the available documentation.

Evidence for this section
  • “two day chain driven. Fusee movement with compensated detent escapement and Harrison maintaining power.”

Open research questions

  • Do Thomas Mercer production records verify the serial number 28400?
  • Does the inclusion of the St. Albans location on the dial provide a more specific manufacturing window?

Source evidence

Recorded claims and source quotations for Thomas Mercer Two-Day Marine Chronometer
FieldSource-reported valueSource quotation
Movement typeTwo-day chain-driven fusee movement“two day chain driven. Fusee movement with compensated detent escapement and Harrison maintaining power.”
Case materialMahogany“The Mahogany case with glazed viewing window and brass gimble”
Case dimensions18.5 cm wide“Box is 18.5cm wide”
Included keyTipsy winding key“having original tipsy winding key”
Estimated Era20th Century“THOMAS MERCER, A 20TH CENTURY TWO-DAY MARINE CHRONOMETER”

Visible details

  • Dial features Arabic numerals for hour markings rather than the Roman numerals stated in the auction description
  • Signed 'Thomas Mercer' across the center and inscribed '28400' on the lower subsidiary seconds dial
  • Signed 'THOMAS MERCER LTD ST ALBANS ENGLAND' at the bottom rim of the dial
  • Gimbaled brass bowl is fitted inside a square wooden case alongside a brass winding key set in a corner mount
  • Upper subsidiary dial is calibrated for up to 56 hours of wind

Research qualifications

  • Auction cataloguer text mistakenly reports the dial as having Roman numerals, whereas the dial visibly displays Arabic numerals
  • Movement is not visible in the photograph; mechanical escapement and fusee details are source-reported

Photograph identity and source facts were screened before import; rights clearance remains pending.

Consulted source

Thomas Mercer, A 20th Century Two-day Marine Chronometer - Jan 25, 2024 | Hutchinson Scott Auctioneers In North Yorkshire

Reviewed 2026-10-21 · Record debbed5435

Terms in this record

Glossary explanations for terms named in this object’s record.

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