Until the 1950s, accurate time measurement was based on the apparent movement of the stars and planets. Today we put crystals and atoms at the heart of our precision timekeepers. When an electric current is passed through a quartz crystal, it vibrates at a very precise frequency and creates a regular pulse for a clock mechanism. Quartz oscillators were first developed in the 1920s by radio engineers searching for accurate frequency sources. By the 1940s, quartz clocks had replaced pendulum regulators in the world's observatories.

This early General Post Office clock was used after 1945 for time signal transmissions from Rugby Radio Station and in the 1960s and 1970s was used in technical colleges as a teaching device. In 2006 it was restored to full working order by electrical and horology specialist, George Hammond, as a gift to the Observatory for the benefit of future researchers and visitors.