The Ronda 315P watch movement is a variant of the 1604 movement with an adjustable stud carrier and a combined setting for the escape wheel lubrication known as Lubrifix. It differs from the 1604 movement in terms of bridge shapes. The specific differences between the 1604N and the 1637N movements are not known. This movement is manually wound and features a sweep second function. It was commonly used around the year 1960.