Watches + Dictionary = Watchionary
Spring Drive
Grand Seiko Spring Drive 5 Days Caliber 9RA2,
Spring Drive

A spring drive is a type of watch movement that combines mechanical and quartz technology to provide a high level of accuracy and a smooth, sweeping second hand motion. It uses a mainspring to store energy, a quartz crystal oscillator to regulate the release of that energy and a stepping motor to move the hands of a watch.

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