Thomas Mercer, Eywood Rd, St Albans. No 14519

Rare complete Patent OCTO 2-day survey chronometer operating minute or seconds electric contacts. Circa 1936.

Case

Strong 2-piece aluminium bound and cloth covered box retaining its original leather pouch containing the winding and hand setting keys, as well as a paper tape showing the results of this chronometer. Rubber mounts inside holding a 2-piece metal canister with stop/start lever acting on the balance, with internally mounted wiring contacts that connect with 'make and break' wheel in the movement.

Dial

Silvered dial signed Thomas Mercer Group prize Neuchatel. 1923 Maker to the Admiralty. Eywood Rd St.Albans. with with cut out showing the action of the minute and seconds contacts, the dial marked out for 24 hours and also noting that this instrument has auxiliary compensation and that the blued-steel hands should only ever be set forward.

Movement

Fullplate fusee movement of typical pre-war Mercer manufacture, the same top quality as their standard 2-day machines intended for marine use. Earnshaw spring-detent escapement, the detent of standard footed form with gold passing-spring. 12-turn Palladium balance-spring paired with Poole's form of auxiliary balance, as occasionally used by the Mercer firm.

Box approx 11 x 8 x 7 inches (28 x 20 x 17.5 cm)

The firm of Thomas Mercer are better known for their marine chronometer work but they were pioneers in the adaptation and use of electrical contacts used on both survey work operating a tape chronograph and on ocean liners where the time shown by a great many clocks (nearly 900 on the Queen Mary) were usually controlled by just two Mercer chronometers such as this. The new Patent OCTO Electric Controlled Clock System was launched in 1923, no doubt helped by Mercer's being awarded the 'Group Prize' at the 1923 Neuchâtel Chronometer Trials. The four 2-day machines shown were all equipped with Poole's auxiliary balances, as here.