What it is
Guilloché (pronounced "ghee-oh-shay") is the French name for the engraved patterns you see on Breguet dials, F.P. Journe dials, the inner zone of a Patek Calatrava 5170, the case-side of a Lange Datograph, or, most famously, the back of a Fabergé egg. The technique itself goes back to 16th-century goldsmiths, who used it to add anti-counterfeiting texture to coins and decorative objects. Watchmakers adopted it in the 18th century; Abraham-Louis Breguet made it a signature of his pocket-watch dials, and the modern association of guilloché with high-end watchmaking traces almost entirely back to him.
How a rose engine works
A rose engine lathe is a hand-cranked machine. The dial blank is fixed to a rotating chuck. A cutting tool (a "graver") sits against the dial, fed by hand-cranked screws. As the dial rotates, the chuck simultaneously moves side-to-side along a programmed cam ("rosette"); this lateral wobble is what produces the wave, basket-weave, or sun-ray pattern. Different rosettes give different patterns. The operator controls feed depth and rotation speed entirely by hand and feel. A skilled engraver can produce one dial per day; mistakes are unrepairable, the dial is scrap.
Common patterns
Clous de Paris (hobnail, small pyramids, the texture on the inside of a Patek Calatrava bezel and on the AP Royal Oak Quantième Perpétuel sub-dials). Vagues de Genève (Geneva waves, parallel zigzag lines). Soleil (sun-ray radial lines). Tapisserie (the classic AP Royal Oak large/grande grid; technically a guilloché variant though AP describes it as separate). Barleycorn (parallel diagonal grain, common on Breguet dials). Damier (checkerboard). The pattern depth on a hand-cut dial is typically 0.05-0.15 mm; the fineness of the lines is what catches the eye.
Hand-cut vs stamped vs CNC
The watch industry uses the word "guilloché" for three different production processes. Hand-cut on a rose engine: the original art, ~CHF 1,000-3,000 per dial in finishing cost alone, used by Breguet, FP Journe, Voutilainen, and Roger Smith. Stamped (struck): the dial blank is pressed under a hardened die that imprints the pattern in a single stroke; cheap, fast, common on many "guilloché-effect" dials. CNC-engraved: a computer-controlled cutting machine traces the pattern; quality varies. Up close, hand-cut shows tiny human-hand variations and depth differences; stamped is uniformly flat; CNC is uniformly perfect (a giveaway in itself). All three are sold under the same word in marketing.
Modern flag-bearers
Breguet is the brand most associated with guilloché; almost every Breguet dial today carries some hand-engraved guilloché pattern, and the brand even runs its own rose-engine workshop in the Vallée de Joux. F.P. Journe uses gold guilloché dials on most Souveraine pieces, distinct because the pattern is on a solid gold dial. Kari Voutilainen hand-cuts every guilloché dial his workshop produces. H. Moser & Cie uses fumé guilloché on top-tier pieces. AP's tapisserie is guilloché-adjacent. Outside watches, guilloché lives on in fountain pens (Montblanc, Pelikan), engraved firearms, and goldsmithing.
How to spot quality
Look at the centre rosette (the geometric "eye" at the centre of the pattern): on a hand-cut dial, the rosette is precisely concentric and the pattern radiates outward without any visible joins. On a stamped dial, the centre often has a slight domed-look or the pattern is visibly soft. Look at the edges: hand-cut patterns terminate cleanly into the chapter ring; stamped patterns sometimes overshoot or have pressure marks. Under raking light, hand-cut shows depth variation, stamped is uniform. For more dial vocabulary see sandwich dials, meteorite dials, or our main guilloché wiki.