Noticeable in the caseback, the oscillating mass in the movement is delicately engraved. It is actually produced from eighteen-karat gold and decorated by hand with a barley grain pattern, accomplished by guilloche If the Omega has the words 'Master Chronometer' on the dial—as is found in the Seamaster Diver 300M—you https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/