automatic: Manual or hand winding In this type the wearer must turn the crown periodically, often daily, in order to wind the mainspring, storing energy to run the watch until the next winding. Automatic or self-winding In an automatic watch, including in most mechanical watches sold today, the mainspring is automatically wound by the natural motions of the wearer's wrist while it is being worn, eliminating the need for manual winding. Additionally, a distinction is also sometimes made on whether or not the movement offers hacking, allowing the second hand to be stopped. Caliber In horology, "caliber" refers to the specific internal mechanism of a watch or clock, also known as a movement. Although the term originally was only used to refer to the size of a movement, it is now used to designate a specific model (although the same caliber can be used in many different watches or clocks). Different watch manufacturers tend to use their own identification system to number their calibers. See also Clockwork Chinese standard movement Spring Drive References External links Federation of the Swiss Watch Industry: Glossary Easy Guide to Watch Movements Caliber Guide Titan Watch Movement Manufacturer Movement (clockwork) Articles containing video clips