Two-day Marine Chronometer by Thomas Mercer, no. 12827
Record status
Individual type · partial
Period
1860-1930
The Science Museum Group collection holds this two-day marine chronometer made by Thomas Mercer in St Albans. Preserved under object number 1931-716, the instrument is housed within an ebony timber case fitted with corner stringing, flush brass carrying handles, and an inset mother-of-pearl plaque on the lid.
The chronometer bowl rests in a brass gimbal mount alongside a locking mechanism. The dial shows Roman hour numerals, blued hands, an up-and-down state-of-wind indicator below XII, and an expanded subsidiary seconds dial above VI. Museum records list construction materials including brass, mother-of-pearl, glass, elinvar, and ebony.
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
- Two-day marine chronometer
- Maker
- Thomas Mercer
- Serial Number
- 12827
- Place recorded
- United Kingdom
- Maker / attribution
- Thomas Mercer
- Place of Manufacture
- St Albans
- Case Dimensions (Closed)
- 194 mm x 189 mm x 193 mm
Design
- Visible features
- • Chronometer bowl suspended in a brass gimbal ring inside an open hinged wooden case. • Silvered dial marked with Roman hour numerals, subsidiary seconds dial above VI, and state-of-wind indicator below XII. • Upper lid features a plain rectangular mother-of-pearl plaque and an interior glazed viewing window reflecting the dial. • Wooden case is bordered with double line stringing and brass corner reinforcements, with a brass keyhole escutcheon on the front face.
- Casing and Physical Construction
- The chronometer bowl is suspended in a brass gimbal ring inside an open hinged wooden case. Closed case dimensions are documented as 194 mm in depth, 189 mm in width, and 193 mm in height, alongside another set of recorded measurements: depth 190 mm, height 190 mm, and width 180 mm. The wooden case is bordered with double line stringing and brass corner reinforcements, with a brass keyhole escutcheon on the front face. Its upper lid features a plain rectangular mother-of-pearl plaque and an interior glazed viewing window reflecting the dial. Listed materials in the museum catalogue include brass (copper, zinc alloy), mother-of-pearl, glass, elinvar (alloy including nickel, steel and chromium), and ebony.
- Identity and Documented Provenance
- This two-day marine chronometer, catalogued under object number 1931-716 by the Science Museum Group, is attributed to maker Thomas Mercer of St Albans and is identified in the title with number 12827. Museum documentation records a credit line to Thomas Mercer Ltd., though comprehensive acquisition details are not provided in the entry. The object is recorded as a chronometer type under the category Time Measurement, with its housing described as an ebony case.
- Source Discrepancies and Limitations
- The museum record presents conflicting chronological data within the same catalogue entry: the 'Made' field states '1850-1880 in St Albans', whereas the title cites '1860-1930'. The source explicitly notes that records undergo ongoing revision and that the institution cannot guarantee the accuracy of information shown on the website. Internal mechanical components, such as any specific balance parts related to the listed elinvar alloy, are not detailed beyond the general materials list.
Identification
- Object Number
- 1931-716
- Serial number
- 12827
- 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: Dating is ambiguous in the source, which gives both '1850-1880' and '1860-1930'.
- Research required: Internal movement components, including the elinvar balance reported by the museum, are enclosed within the brass bowl and not visible.