The Tissot 2591 watch movement, manufactured from 1973 to 1980, features a ratcet wheel made of beryllium bronze. It holds the distinction of being the smallest ever industrial manufactured automatic movement, in terms of volume. This movement consists of a manual-wind base movement and an automatic module that is screwed onto it. The compact design allows for a reduced total height. Additional functions of the movement include an adjustable stud holder, automatic winding, and Incabloc shock protection.