Balance

The balance wheel

The balance wheel is the clock-setting part of a no longer stationary wheel clock (e.g. a pocket watch). The name came about after 1675, when Christiaan Huygens introduced the pendulum and the spiral spring as a regulator in his patent.

Its predecessors were the Unrast with scales and the torsion spring that Peter Henlein used in his can clock in 1505.

Image: Chris Burk's Wikipedia