At the “heart” of the watch, the balance-wheel and balance-spring guarantee the watch’s accuracy. Because of its importance, the Poinçon de Genève specifies that the balance-spring fixing must be elegant, and prohibits the use of glue.
This system is positioned between the wheel train and regulating organ. Being essential to the correct functioning of the watch, the Poinçon de Genève specifies that it must have impeccable finishes. It also specifies its maximum thickness depending on the diameter of the movement.
- For movements with a total diameter of more than 18 [mm]:
The thickness of the escape-wheel must not exceed 0.16 [mm]. The locking-faces of its teeth must be polished.
- For movements with a total diameter of less than 18 [mm]:
The thickness of the escape-wheel must not exceed 0.13 [mm]. The locking-faces of its teeth must be polished.
The angle described by the lever must be limited by fixed banking-walls to the exclusion of pins or studs.
Stud and adjustment index
These two components are related to the operation of the balance-spring. The stud is used as an attachment, while the adjustment index is used to modify the watch operation by altering the length of the balance-spring. There are many systems to hold the balance-spring in place, but only the most elegant are permitted and they are subject to strict conditions.
1. The balance-spring may be pinned up with a grooved plate having a rounded collar and cap.
2. A mobile stud holder is acceptable as long as it can be locked in position.
3. Split or fitted indexes are allowed with a holding system except in extra-thin calibres where the holding system is not required.
4. Balance-wheels adjusted by variable inertia are acceptable.