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The mainspring was in vented and put into watches to increase the torque of early watches. https://www.britannica.com/technology/watch
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Early examples of the watch are by Peter Henlein, in Germany Nürnberg. The first watches were used the same as early clocks. https://www.britannica.com/technology/watch
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Until 1580 only iron was the only material in watches then watchmakers tried brass and after that it became mainstream