different bridge shapes
Option: Incastar regulator /Fig.7):
The only large-scale produced regulator featuring a free oscillating hairspring. The end of the spring is fixed between two rollers, adjusting actually its length (photos at the bottom). No isochronism error by the gap between the regulator pins.
option Triostat regulator (Fig.10, 11):
unit with three adjustment features: precision adjustment for speed and regulator pin-width, as well as mobile stud carrier
differences not known between 72, 72-6, 72-7, 721, 723, 725, 725-7