The automated COSC-Qualified PF441 chronometer movement that this Parmigiani traditional operates on provides a 55-hour electric power reserve, owing to its oscillating mass, which happens to be in delicately engraved gold, and may be admired through the sapphire crystal caseback. And admire it you will, since it shows a lot https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/