A precision clock is a clock designed to keep time with the greatest possible accuracy, typically for scientific, astronomical or professional use. The best-known type is the regulator, a weight-driven pendulum clock with a plain, legible dial, used in observatories, workshops and by watchmakers as a standard against which other timepieces were set.
The pursuit of precision timekeeping advanced rapidly in England in the late seventeenth and eighteenth centuries. George Graham's deadbeat escapement and mercury-compensated pendulum reduced errors caused by friction and temperature, while John Harrison and later makers developed gridiron pendulums and other refinements. Fine regulators by makers such as Vulliamy, Dent and Frodsham were produced through the nineteenth century, and in the twentieth century free-pendulum clocks such as the Shortt system set new standards. A precision clock is usually recognised by its seconds dial, jewelled or high-quality pallets, maintaining power, heavy pendulum and austere, well-made case, often with a glazed door to show the movement. Collectors value originality, signed movements and a documented history of use. Such clocks combine engineering excellence with understated elegance and suit a library, study or hall.
