Watch movement of iron with gilt metal case; Germany, c. 1550; dia. 2” (5.08 cm.).
The earliest watch movements were iron and somewhat roughly finished; then, decoration was applied only to the case.
In Germany, the varying power of the spring was usually modified by a brake (‘Stackfreed’) which is shown here. The arbor for the spring has a pinion which meshes with a wheel carrying a special cam. Some of this wheel’s edge is uncut to limit the turns of the pinion and thereby the winding of the spring. The roller is pressed against the edge of the cam by its spring, resisting it when fully wound, aiding it when nearly run down.
