The Tissot 28.5R-21 watch movement is an antimagnetic version of the 1570 movement, specifically developed for the Milgauss model. It features a free Breguet hairspring and a balance with regulating screws. The movement includes the following functions: automatic winding, sweep seconds, and a hack feature. It also has a stop seconds function and incorporates a sweep seconds hand. The 1580 movement was used during the period from 1965 to 1974.