The automated COSC-Qualified PF441 chronometer movement that this Parmigiani classic runs on provides a 55-hour energy 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 may, as it shows some of the greatest decoration https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/