The knob on the outside of the watch that you typically use to either wind the mainspringMainspring The mainspring is a spiral-shaped metal spring that stores energy in a mechanical watch movement. It is located inside the barrel, a cylindrical container. The mainspring is wound by the wearer, either manually or automatically, through the movement of the wearer's wrist. The mainspring is the source of energy for the watch, and the tension in the mainspring determines the power reserve. The mainspring unwinds over time, and the watch will stop running when the mainspring is fully unwound. [Learn More] or set the time

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