668 movement is a mechanical movement developed and produced by China Watch Manufacturing Company Tianjin Watch Factory (now renamed Tianjin Haitai Watch Co., Ltd.) in 1960s. It is an automatic winding movement, which adopts automatic winding design to provide energy for the movement of the wearer's wrist. It consists of metal parts, gear system, clock spring, balance wheel, etc. It realizes the function of measuring and displaying time through precise mechanical structure. In the watch industry in China, 668 movement has a certain popularity and is widely used to manufacture various types of watches, including mechanical watches, pocket watches and desk clocks.