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The Encyclopedia of Horology

Marine chronometer · Two-day marine chronometer

Thomas Mercer Marine Chronometer No. 19780

Partially verified

This marine chronometer by Thomas Mercer Ltd. of St. Albans, England, is mounted in a gimballed brass bowl housed within a glazed wooden deck box. The silvered dial features black Roman hour numerals, blued hands, an up-and-down state-of-wind indicator below the twelve o'clock position, and an auxiliary seconds dial at six o'clock inscribed with serial number 19780. A brass plaque mounted on the front edge of the wooden box lid notes distribution by N.V. Observator in Rotterdam alongside number 19780. The lot retains its brass gimbal locking mechanism and winding key.

Thomas Mercer marine chronometer No. 19780 in gimballed brass bowl and wooden box
Thomas Mercer marine chronometer No. 19780 in gimballed brass bowl and wooden box — Bolland-Marotz. Rights pending — permission not yet requested. Original source

Catalogue identity

Source
www.invaluable.com
Category
Marine chronometer · Two-day marine chronometer
Maker / attribution
Thomas Mercer Ltd.
Reference
Not recorded
Catalogue / lot identifier
766
Source-reported date
Not established
Country
United Kingdom
Source-reported serial
19780

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 Configuration and Inscriptions

The marine chronometer features a silvered dial marked with Roman numerals and blued hands. The register configuration includes an up-and-down indicator situated beneath the 12 o'clock position and an auxiliary seconds register at 6 o'clock.

The dial is inscribed with the maker and serial designation "Thomas Mercer LTD. St. Albans, England 19780". Although the auction lot heading lists "Nr. 17832", the dial itself explicitly bears number 19780.

Evidence for this section
  • “Auf dem versilb. Ziffernblatt mit röm. Zahlen bez. ''Thomas Mercer LTD. St. Albans, England 19780''.”
  • “kl.Sek.,flex. Auf- u. Abanzeige bei der ''12'' und kost. Sek. bei der ''6''; gebläute Zeiger.”

Casing and Mounting

The instrument is mounted in a gimballed brass bowl (kardanisch gelagertes Messinggehäuse). Observations of the lot record a locking bracket mechanism alongside a winding key positioned in the corner socket of the case.

The outer case is a wooden deck box with brass and metal fittings and glazed aperture glass, catalogued with dimensions of 17 x 19 x 19 cm. A cartouche affixed to the front of the wooden housing is inscribed "Supplied by N.V.Observator ...Rotterdam...No. 19780".

Evidence for this section
  • “Kardanisch gelagertes Messinggehäuse”
  • “Holz, Messing- u. Metallbeschläge; Glas. 17 x 19 x 19 cm.”
  • “Auf der Vorderseite des Holzgehäuses Kartusche mit Bez. ''Supplied by N.V.Observator ...Rotterdam...No. 19780''.”

Source Documentation and Cataloguing Discrepancy

The lot heading introduces an apparent discrepancy by titling the piece with "Nr. 17832", whereas both the dial inscription and the distributor cartouche consistently document number 19780.

Internal movement details, escapement arrangement, balance type, and mechanical operating condition are not recorded in the auction listing, as the movement remains enclosed within the brass casing.

Evidence for this section
  • “Thomas Mercer Marine Chronometer. St. Albans England, Nr. 17832.”
  • “Auf dem versilb. Ziffernblatt mit röm. Zahlen bez. ''Thomas Mercer LTD. St. Albans, England 19780''.”

Open research questions

  • What specific balance and escapement mechanisms are fitted within the enclosed movement of serial 19780?
  • Do historical ledger records from Thomas Mercer Ltd. or N.V. Observator confirm the production date and supply date for chronometer 19780?
  • What caused the discrepancy between number 17832 in the auction heading and serial 19780 marked on the dial and cartouche?

Source evidence

Recorded claims and source quotations for Thomas Mercer Marine Chronometer No. 19780
FieldSource-reported valueSource quotation
Dimensions17 x 19 x 19 cm“17 x 19 x 19 cm.”
Dial inscriptionThomas Mercer LTD. St. Albans, England 19780“Auf dem versilb. Ziffernblatt mit röm. Zahlen bez. ''Thomas Mercer LTD. St. Albans, England 19780''.”
Distributor plateSupplied by N.V.Observator ...Rotterdam...No. 19780“Auf der Vorderseite des Holzgehäuses Kartusche mit Bez. ''Supplied by N.V.Observator ...Rotterdam...No. 19780''.”
MountingGimballed brass casing“Kardanisch gelagertes Messinggehäuse”
HandsBlued hands“gebläute Zeiger”

Visible details

  • Hinged wooden deck box with glazed upper aperture shown open
  • Gimballed brass bowl with locking bracket and winding key placed in the corner socket
  • Silvered dial with Roman numerals, an up-and-down indicator under 12, and subsidiary seconds register at 6
  • Engraved distributor plate affixed to the wooden lid reading 'SUPPLIED BY N.V. OBSERVATOR... ROTTERDAM... NO 19780'

Research qualifications

  • The auction title erroneously states 'Nr. 17832', but both the dial face, description text, and lid plate show serial number 19780.
  • Internal movement is enclosed in the bowl and not visible in the provided photograph.

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

Consulted source

Sold at Auction: Thomas Mercer Marine Chronometer. St. Albans England, Nr. 17832. Holz, Messing- u. Metallbeschläge; Glas. 17 x 19 x 19 cm. - Auf der Vorderseite des Holzgehäuses Kartusche mit Bez. ''Supplied by N.V.Observator ...Rotterdam...No. 19780''. Auf dem versilb. Ziffernblatt mit röm. Zahlen bez. ''Thomas Mercer LTD. St. Albans, England 19780''. Kardanisch gelagertes Messinggehäuse; kl.Sek.,flex. Auf- u. Abanzeige bei der ''12'' und kost. Sek. bei der ''6''; gebläute Zeiger.

Reviewed 2026-10-21 · Record c776d4d414

Terms in this record

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

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