A marine chronometer numbered 462, by McLachlan. It has an eight-day double-frame fusee movement with three pillars, all fixed with blued screws. The movement is marked with the broad arrow. The fusee, with stop-work and Harrison's maintaining power, has a pipe round the winding square. There is an Earnshaw-type spring detent escapement and a two-arm balance with a blued helical balance spring.

The movement is mounted in a three-tier brass-bound mahogany box with a push-catch for the lid and a lock for the upper half. The upper half has a strut limiting opening to 90°. On the front of the upper half is screwed a rectangular tablet inscribed ‘McLACHLAN / 462 / 8 DAY’ and the broad arrow. The box fittings are standard, with brass drop handles on the sides, brass gimbals and a ratchet-winding key. The bowl has a brass balancing weight on the inside. The push-catch and lock are surrounded by shaped brass inserts. There is a cushion-shaped brass insert on the box lid. The underside of the box is covered with green baize. Inside the lid is a brass label-holder containing a rectangular card label and a circular paper label printed ‘Issued from / H.M. Chronometer / Depôt, / Bradford-on-Avon. / 15 OCT 1943’.

A silvered-brass dial has Roman numerals and a large seconds dial has Arabic ten-second figures with straight batons at alternate five-second intervals. The dial is inscribed in the centre ‘McLachlan. London. No 462.’ In the seconds dial is the broad arrow. The up-and-down dial, below XII, is marked with Arabic numerals zero to seven. It is marked 'UP' above zero and 'WIND' above seven. The chronometer is in good condition.

A typical eight-day marine chronometer of the mid-19th century. This type of machine was later largely withdrawn from UK Royal Navy ships in favour of the more accurate two-day version. The maker of this chronometer was probably Hugh McLachlan of Upper Street, Smithfield, London.