Battery-powered tuning-fork-controlled marine chronometer. It is of the 'Accutron' brand of tuning-fork timekeepers.

This marine timekeeper uses three interconnected tuning-fork movements each mounted 120° apart so as to minimize error. The mechanism is sealed in a brass case with rubber 'O' rings to protect against moisture and sudden pressure changes and the whole assembly is attached to a spring-loaded mount to reduce vibration and shocks. The 50 mm dial is divided into 24 hours with Arabic numerals and a centre-seconds hand. The case is a wood-effect plastic veneer on a seasoned timber carcass lined with green baize.

First introduced in 1960, the Bulova Accutron wristwatch was the first electronic watch ever made and the first watch not to use a balance wheel as the timing element. It ranks as one of the most significant technical developments in portable horology in the 20th century and is a crucial 'stepping-stone' between the conventional mechanical watch and the now-ubiquitous quartz-controlled watch. For the whole of the 1960s the Bulova Accutron was a significant player in the quality wristwatch market. The Accutron marine timekeeper was a later spin-off development.

Accutrons are controlled by tiny tuning forks vibrating at 360 times per second, maintained by a transistorized electronic circuit and a battery lasting about a year. Their substantial technical achievement was the micro-miniaturization of the components: the index wheel that is advanced by the vibrating fork is just over two millimetres diameter, yet has over 300 teeth.