A mechanical wristwatch movement (also referred to as a 'calibre' or 'caliber') is the mechanism located in the case of the watch that is responsible for powering it, keeping precise time and carrying out its functions. A movement is either manually wound or self-winding (automatic).

What is a Mechanical Watch Movement? (photo: Rolex)

A manual or hand-wound watch movement is powered by the winding of the crown. The crown winds the mainspring inside, which is the power source of the movement. That power moves through the escapement and is regulated by the oscillator. The oscillator is like the heart of the watch, but instead of pumping blood into the circulatory system it regulates the frequency of energy coming from the mainspring through the escapement.

Rolex innovated the self-winding Perpetual rotor in 1931 to power their wristwatch movements without requiring the wearer to wind the crown. Instead, a semi-circular weighted rotor pivots back and forth as the watch moves on the wrist to wind up the mainspring. The video below does a good job of illustrating the inner workings of mechanical watch movements - both manual and self-winding - as well as quartz movements, which are battery powered.

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