The original clocks used a set of points similar to distributor points that, when closed, charge
a couple of coils turning them into electromagnets. The "magnets" then activate a hammer that
rewinds the mainspring until it ticks down and again closes the points which fires the coils, etc.
The problem is eventually the points fuse together or simply break off. If the points fuse together
the coils gets full battey power and melt. A friend built a circuit board that uses capacitors to fire
the coils when the points close. No full battery power and the points only act as a switch to trigger
the capacitor bank.
mike