Shown is the meter mechanism for a Westinghouse Type-OA watthour meter. I had to remove it to restore the cast iron meter case. The two devices to the left and right, just below the register, are damper magnets. Their magnetic energy exert Lenz Forces upon the disc to regulate it's rate of spin. Without these damper magnets, the disc would spin out of control. Physics plays a big role in the design of these meters.