The Thomas Mercer Chronometer No. 23531 is a historic two-day marine chronometer manufactured by Thomas Mercer Ltd

The Thomas Mercer Chronometer No. 23531 is a historic two-day marine chronometer manufactured by Thomas Mercer Ltd

The Dial: Features a 4.25-inch silvered dial signed by Thomas Mercer Ltd. It includes classic Roman numerals, an outer minute track, a 56-hour power reserve indicator (state-of-wind), and a constant subsidiary seconds dial
The Movement: Powered by a brass full-plate fusee movement with maintaining power. It utilises a highly precise Earnshaw-type spring detent escapement alongside a split compensated balance and a helical hairspring.
Housing: Encased in a brass bowl with a sliding winding-hole shutter, suspended on a gimbal mount. This entire assembly is nested inside a square, glazed mahogany deck box.
Silvered dial
Serving ships had at least 3 of these sometime up to 7
Earnshaws detent escapement
compensation balance
steel helical spring
Blued steel hands.
Vessel Commemoration: The box is fitted with a brass plaque inscribed “Nils.V”, which likely links the instrument to the specific vessel or shipping company it navigated for during or after the war. [1, 2]
In maritime naming conventions—particularly within Scandinavian, Dutch, and German shipping—names formatted with a single-letter suffix typically denote one of two historical origins:
The Owner/Founder Variant:
The “V” is highly likely an abbreviation for a prominent shipping family surname or company. For instance, the Van Uden line or similar Dutch/Belgian operators frequently used short names followed by family initials. Alternatively, “Nils” could represent the ship-owner’s son or the company founder (e.g., Nils Von…).

The Sequential Fleet Variant: Some merchant fleets assigned names alphabetically or sequentially to their cargo vessels or tugboats (e.g., Nils I, Nils II, Nils V), meaning “Nils.V” likely represents the fifth ship in a specific class or fleet design series.
Working order

Measures 17cm high by 18cm wide & 18cm deep