Visible from the caseback, the oscillating mass of the movement is delicately engraved. It's comprised of 18-karat gold and decorated by hand with a barley grain pattern, performed by guilloche A paragon of robustness and dependability, the forty mm Oyster case of The brand new GMT-Learn II is guaranteed waterproof https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/