Visible in the caseback, the oscillating mass in the motion is delicately engraved. It's constructed from 18-karat gold and decorated by hand having a barley grain pattern, carried out by guilloche A paragon of robustness and trustworthiness, the forty mm Oyster case of the new GMT-Master II is certain water-resistant https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/