Flip it over and you have the automatic caliber
link 591C with hand-finished rotor and 169 components. This movement has a slightly lower power reserve than the 537/3 coming in at 38 hours. Again you can see it through the sapphire crystal caseback, and Breguet gets major props here for using such a high
link quality movement (full-stop) and in their
link ladies' watch as well (double full-stop).
link