Visible in the caseback, the oscillating mass of your movement is delicately engraved. It can be made from 18-karat gold and decorated by hand with a barley grain pattern, accomplished by guilloche A gold Variation includes a black dial and black leather strap, and also an eighteen-karat gold pin-buckle Issues: https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/