Engine Turned

Engine Turned refers to a geometric pattern/technique in which metal is engraved  (with a machine that moves in a repetitive turning motion) in order to add depth and a three dimensional design to a flat surface.

Within the "engine turned" design, there are many different kinds, some including different widths of the lines and shapes (such as jagged lines). 

This pattern is most frequently found on English Georgian silverware such as the snuff box below. 

Also See : Guilloche