The automatic COSC-Accredited PF441 chronometer movement that this Parmigiani classic runs on provides a fifty five-hour electrical power reserve, owing to its oscillating mass, which can be in delicately engraved gold, and will be admired through the sapphire crystal caseback. And admire it you might, since it shows a lot https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/