The Longines 18.50 watch movement, which was in use from 1973 to 1976, is the last family of movements designed by MST. While all parts except the calendar discs are interchangeable among the family members, a notable feature is its hacking mechanism, which stops the 4th wheel and, less commonly, the balance. Additionally, it incorporates an indirectly driven minute, enabling a larger balance and a low-profile design. The movement also offers optional excenter device installation on the regulator, a right-handed crown-wheel screw, and features such as manual wind, sweep second, quickset date, Incabloc Shock Protection, and stop seconds function.