Victorian Guilloché Brooch with Translucent Cobalt Blue Enamel. Photo Courtesy of Lang Antiques.

Guilloché is an engraved decoration of concentric design made on metal through the use of a lathe resulting in an engine-turned effect. This engraving is often covered by translucent enamels to highlight the pattern. This technique was especially popular around the fin-de-siecle period. Carl Faberge was a master at using the guilloché technique and used it extensively in his jewelry, clocks and other objects de virtu.