Pre-balance-spring era watch movement by Thomas Tompion, with a long screwed-on balance cock and worm-and-wheel set-up. A high quality fusee movement, with no pinion having less than 6 leaves. Signed 'Thomas Tompion, London' in flowing script c.1671

The application of a balance spring to a watch, which had the effect of greatly improving its timekeeping, was independently developed by both Robert Hooke and Christiaan Huygens, with Huygens patenting a watch with his design in 1675. Hooke denied Huygen's invention, claiming that he had devised it in London in 1658.

Hooke commissioned Thomas Tompion to make a watch containing the device, which was signed ‘R. Hooke invenit an. 1658. T. Tompion fecit 1675’.

All subsequent watches by Tompion contain a balance spring; this movement is very important as it is the only known watch by him of the pre-balance-spring era.

Clockmakers' Museum No. 39