The polished blue bi-directional rotating bezel is compelete with a vivid orange GMT scale and helium-escape valve at 10 o'clock on the case. It requires the melting of the Uncooked compound applying oxyhydrogen flame and the crystallisation from the melted droplets to sort a cylinder. Graded nine to the Mohs-hardness https://www.watchesworld.com/top-10-dive-watches/