2. A clock is a timing device, a precise instrument for measuring and indicating time. Clocks are usually distinguished by the size of the internal machine. According to international practice, clocks and watches with a movement diameter greater than 80 mm and a thickness greater than 30 mm; A pocket watch with a diameter of 37 ~ 50 mm and a thickness of 4 ~ 6 mm is called a pocket watch; Watches with a diameter less than 37 mm; A watch whose diameter does not exceed 20mm or whose movement area does not exceed 3 14m2 is called a women's watch. The watch is one of the smallest, strongest and most sophisticated machines invented by human beings.
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