18k (750 thousandths) yellow gold navette-shaped watch ring set with rose-cut diamonds. Transparent red guilloché enamel top engraved with gold lines showing extraordinary technique. Enamel hour dial in excellent condition. Openwork ring running the length of the case, ending in arrow-shaped shoulders, revealing a perfectly engraved, thick tray support to accommodate the watch mechanism. The raised, beveled crystal is in excellent condition. Mid-19th century. Manual mechanical movement with key (present). Enamel dial with blue and red colored numerals. Gilded dotted minute divisions. Cylinder escapement. Adjustment and winding access via a remarkable slide bar under the caseback. Very good condition. Functional at time of appraisal. Finger size : 54 Gross weight: 16.2 g. Expert's note: The art of guilloché originated in the 18th century. It is a mechanical process of engraving on gold or silver by a guillocheur, a machine that engraves geometric patterns using cogwheels and cursors. This creates highly precise, regular and repetitive patterns. In the case of this watch, the surface is very small. To add complexity to the work, very fine gold wire decoration is applied and the whole is enameled to perfection. This is haute joaillerie as well as haute horlogerie. Don't hesitate to ask the expert for his magnifying glass to delve into these remarkable details.