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The Encyclopedia of Horology

Marine chronometer · Ship's marine chronometer

Asmus Johanneson 56-Hour Ship's Marine Chronometer

Partially verified

According to dealer documentation, this antique marine chronometer is signed by London maker Asmus Johanneson and houses a 56-hour movement. The instrument is gimbal-mounted within a three-tier brass-bound mahogany deck box featuring recessed side handles and a locking mechanism. Its engraved, silvered dial displays Roman numeral hours, a subsidary seconds register, and a power reserve state-of-wind indicator positioned below twelve o'clock. An original ratcheted winding key is docked in the upper corner of the case interior. The seller dates the chronometer to circa 1900–1920, with external dimensions measuring 19 cm in height, 19 cm in width, and 17 cm in depth.

Oblique view of the open three-tier mahogany deck box showing the gimballed brass bowl, dial, and winding key
Oblique view of the open three-tier mahogany deck box showing the gimballed brass bowl, dial, and winding key — Quiet Street Antiques of Bath. Rights pending — permission not yet requested. Original source

Catalogue identity

Source
www.sellingantiques.co.uk
Category
Marine chronometer · Ship's marine chronometer
Maker / attribution
Asmus Johanneson
Reference
1618
Catalogue / lot identifier
SA522445
Source-reported date
1900 - 1920
Country
United Kingdom

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 Suspension

The instrument features a brass bowl suspended within a gimbal system held in an open mahogany deck box. The silvered dial incorporates black Roman numeral hour markers, an auxiliary running seconds register, and an "Up-and-Down" state-of-wind indicator dial set directly below Roman numeral XII.

Mounted adjacent to the suspension ring in the top corner of the box interior is a slotted ratcheted winding key, while a gimbal locking lever is positioned along the side of the mounting ring to secure the mechanism during transport.

Evidence for this section
  • “Chronometer movement bowl mounted in a brass gimbal suspension within an open mahogany box”
  • “The engraved & silvered dial is signed, and features a seconds dial and an "Up-and-Down" dial below "XII".”
  • “It opens to reveal the 56-hour movement set within gymbals, with locking lever and original ratcheted winding key.”

Box Construction and Hardware

The chronometer is housed within a three-tier mahogany box fitted with protective brass corner reinforcements, external hinges, and a central brass keyhole escutcheon on the upper case segment. The lower tier incorporates flush-fitted recessed brass side plates and carrying handles designed for shipboard stowage.

Externally, the box measures 19 cm in height, 19 cm in width, and 17 cm in depth according to dealer physical specifications.

Evidence for this section
  • “The good three-tier mahogany case is bound in brass, with recessed brass side handles.”
  • “Brass corner reinforcements, hinges, keyhole escutcheon, and recessed side plate on the mahogany case”
  • “Height 19cm (7.48") Width 19cm (7.48") Depth 17cm (6.69")”

Maker Attribution and Documentation Limits

The seller attributes the chronometer to Asmus Johanneson of London, dating the instrument broadly to 1900–1920 or the 1900s. Johanneson is noted by the dealer as the head of a firm at 149 The Minories that supplied chronometers to the British Admiralty between 1890 and 1910.

No internal movement photographs, escapement details, plate engravings, or instrument serial numbers are documented in the listing. Claims of internal mechanical completeness, full operational status, and specific Admiralty affiliation rely entirely on dealer statements and are not verified by photographic evidence.

Evidence for this section
  • “by Asmus Johanneson of London”
  • “Danish born Asmus Johanneson was head of the London firm (based at 149 The Minories) which had a fine reputation for chronometers, supplying the Admiralty with them from 1890-1910.”
  • “Quiet Street Antiques of Bath has dated this piece to the 1900s.”

Open research questions

  • What specific serial number and signature text are engraved on the movement plates and dial face?
  • Does the movement utilize an Earnshaw spring detent escapement and an auxiliary compensation balance?
  • Are there Admiralty broad arrow marks or official hydrographic service issue numbers stamped on the brass bowl, gimbal, or dial?

Source evidence

Recorded claims and source quotations for Asmus Johanneson 56-Hour Ship's Marine Chronometer
FieldSource-reported valueSource quotation
MakerAsmus Johanneson of London“by Asmus Johanneson of London”
Case constructionThree-tier mahogany case bound in brass“The good three-tier mahogany case is bound in brass, with recessed brass side handles.”
Movement56-hour movement in gimbals with locking lever“It opens to reveal the 56-hour movement set within gymbals, with locking lever and original ratcheted winding key.”
Dial descriptionEngraved and silvered dial with seconds and up-and-down registers“The engraved & silvered dial is signed, and features a seconds dial and an "Up-and-Down" dial below "XII".”
Dealer Internal Reference1618“Dealers Internal Reference 1618”
Maker Business Address149 The Minories, London“based at 149 The Minories”
Dealer Operational Date RangeCirca 1900s / 1900–1920“Quiet Street Antiques of Bath has dated this piece to the 1900s.”

Visible details

  • Chronometer movement bowl mounted in a brass gimbal suspension within an open mahogany box
  • Silvered dial with Roman numerals, a subdial for running seconds, and an up-and-down state-of-wind indicator below XII
  • Gimbal locking lever and corner-mounted winding key clearly visible in the case interior
  • Brass corner reinforcements, hinges, keyhole escutcheon, and recessed side plate on the mahogany case

Research qualifications

  • Internal movement plates, balance assembly, escapement, and serial numbers are not pictured or specified
  • Attribution to Asmus Johanneson, operational status, and date range rely on dealer claims

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

Consulted source

56-Hour Ship's Marine Chronometer | Sellingantiques.co.uk

Reviewed 2026-10-21 · Record 24affbf0d1

Terms in this record

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