This movement is an example of a mechanically switched moving coil balance wheel. The magnets are arranged in a circular pattern and are fixed to the clock frame, and the coils are mounted on the balance wheel. One coil contact is through the balance wheel, hair spring and clock frame, and the other is through an insulated pin on the under side of the balance wheel which touches a flat spring contact on each swing. Mechanical switching of the current to the coils is subject to fluctuations due to a build up of dirt and corrosion of the contacts. Over time this can make the clock lose accuracy.
Drive to the hands is via an inverted Sully escapement. The movement dates from the late 1960s.
