In watchmaking, decoration is not mere ornament: it is visible proof of manual work and mechanical precision. I have spent decades dismantling movements and examining plates under magnification, and the first thing I learn to read in a caliber is the quality of its finishing. A bridge with poorly executed Côtes de Genève tells you more than any technical sheet.
The Côtes de Genève — also called Geneva stripes or, in its German variant, Glashütte striping — are wavy parallel lines engraved on plates and bridges. In Geneva they often run radially; in Glashütte they tend to be narrower and denser. They do not protect the metal significantly: their purpose is to show that someone took care. Perlage (or graining) works differently: thousands of overlapping small circles, created with rotating burrs, produce an opaque surface that absorbs light and hides scratches. It is usually applied to surfaces not visible at caseback, but in the most attentive manufactures you find it on the inner face of plates too.
Guillochage is the richest territory. With the rose engine, geometric patterns are engraved on the surface — barleycorn, waves, herringbone, regular dots — that come alive with wrist movement. Clous de Paris is one of these patterns: a grid of small pyramids. Azurage produces instead finer wavy parallel lines, often on subdials. Guillochage can be applied to the dial, the plate, the caseback, the rotor: Voutilainen carries it on the dial gold with the historic machinery of the Comblémine manufacture; Czapek uses it to create optical illusions of depth on titanium together with Metalem.
Other techniques have older roots. Engine turning is a form of mechanical guillochage that produces regular geometric patterns — concentric circles, radial, chevron — and was already present on cigarette cases and tobacco boxes in the interwar decades. Gadroons are raised flutes alternating with brushed surfaces, used by Piaget since the Seventies to enliven flat cases. Snailing creates concentric spirals similar to a snail shell: you find it often on vintage dial flanges or on minute tracks.
Hand chamfering (anglage) is the finishing most difficult to judge in photography: you must hold the piece in hand and turn it under light. An edge chamfered by hand with wood and abrasive paste produces a continuous mirror without interruptions. Done by machine, the reflection breaks. That's where you see the difference.