TAG Heuer just introduced a watch with a magnet as the balance wheel. (It is the highest beat production watch ever made.) Of course, magnets and balance wheels have been married for a long time... (TAG's innovation is no hairspring) ...and here is some evidence:
In the 1960's Timex introduced the Caliber 870 a robust implementation of the electric watches of that era. It was made in "West Germany".
To generalize, the electric watches have a coil on the balance 'wheel' that is pulsed with current during one arm swing of the arc. This creates a repulsive magnetic field to the permanent magnets fixed to the mainplate. The repulsive field provides a kick to the balance wheel to give it some energy. That energy is channeled by the escapement into the drive train.
The wheel rotates backwards to another point where the next pulse is applied. Thus there is an energy pulse each arc of the balance wheel. There is a hairspring attached to the balance wheel to regulate the timing of these arcs.
Normally the mainspring is providing power into the gear train and the escapement regulates the application of the power. In this design the power is coming directly from the escapement. (That thick piece of brass at the bottom of the next picture is part of the balance wheel!)
Beyond that, they are normal watches.
As I said, the Timex implementation was a robust one using a thick stamped and machined plates. Plastic was used when appropriate and it appears the intervening fifty years has not aged it. The screws are not delicate nor dainty. But the assembly was accurate. All of these production savings allowed Timex to offer these watches for $25 or less.
Notice the size of the 'hairspring'... no need to conserve energy in this design (and it had better be non-magnetic!).
This is a side on view of the balance wheel. It is the beefy chunk of brass you see. Below it is a ferrite permanent magnet.
The Caliber 870 is called the Model 84 in Timex technical documentation. Evidently the Service department did not appreciate the marketing department ruining their numbering schema and they just renamed the movement.
I have seen this movement in a number of Timex watches and earlier this year we even had a member asking how to open the caseback. I suspect it is one of their last electrics but I am only just starting to learn about them.
This specific watch looks like it can be coaxed into maybe 30 seconds per day accuracy (from the vendor it is at +120 spd). The movement is clean and the timing screen shows no irregularities in the beat.
Just to complete the documentation, two views of the caseback. It is epoxied to the rest of the case.
The inside of the caseback... note the easy match of the "crown" to the green knob on the movement. Putting the movement back in the case is trivial.
And to round out - a mystery! ... strange dial numbers