There's a lot to be said about autos, here is just a little. Above is a bumper automatic movement. The sickle-shaped weight stamped "Military" is the rotor. It moves back and forth, and is connected centrally to a sort of axle. By moving back and forth, it winds the mainspring. To the right, you can see one of the fixed springs which cushion the rotor as it comes around. This can cause a tactile sensation to the wearer, as the rotor smacks into spring. I really like the bumper auto.
Abraham Louis Perrelet built the first self-winding watch, a pocket watch, in 1770. The watch at left is called "Perpetuale," from 1890. The hammer on the left was said to have wound the movement.
The Harwood watch, right, was the first commercially produced automatic watch. Produced in 1926, the Harwood auto had no winding crown, but instead had a coin-edge type of ring around the bezel which set the hands. You could not "jump start" the movement with the winding crown, as in most later autos. The lack of a winding crown was said to be key in keeping out dust, which was considered evil to watches. Harwoods were fussy, few were made. Today, a working Harwood brings in a lot of money, and even the broken ones don't do too shabbily. Here's an article about early autos, including Harwood, Autorist, Rolls.
(I do not own this Harwood, came from Web picture)
Dialing a telephone is enough to wind an automatic watch, said this ad from the "Federation of the Makers of Fine Swiss Watches." There was a bit of a greater challeng to make an efficient auto winding ladies watch, because of the smaller size of the rotor.
Here's an x-ray of a bumper automatic watch. Click here for more xrays.