British precision tank regulator, c.1960

Overview

This clock was made by John Godman, working for T & F Mercer, to an earlier design by E. T. Cottingham. It is an observatory-grade regulator with a brass bob Invar pendulum in a grey steel vacuum tank under a round glass dome. The impetus for this clock came from a complaint from the British Admiralty, who objected to using a German-made Riefler clock in the Greenwich Observatory. This is one of several British variants on Riefler’s design developed in response; it incorporates a double wheel escapement, with impulses to the pendulum given through the suspension spring, and an electrically reset remontoire.