The automatic COSC-Qualified PF441 chronometer movement that this Parmigiani classic operates on provides a 55-hour electrical power reserve, owing to its oscillating mass, which is in delicately engraved gold, and may be admired from the sapphire crystal caseback. And admire it you'll, as it shows some of the finest decoration https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/