This experimental watch is housed in a gold case and has a white enamel dial typical of French watches of the period. The main interest, however, lies in the movement and Berthoud's use of a gridiron compensator. The movement is conventional, with a fusee and verge escapement controlled by a gilded-brass three-arm balance and spiral balance spring. To compensate for the effects of temperature change, Berthoud used a simple gridiron of six steel rods and six brass rods mounted in a frame. To compensate for changes in the elasticity of the balance spring, caused by changes in temperature, the gridiron acts, via a lever, on the spring's outer end, altering its effective length.

место:
Room 38-39: Clocks and Watches

Ferdinand Berthoud Inv et fecit 1763 (around the edge of the dial plate)

Ferdinand Berthoud a Paris No 417 (on the back plate)