Guilloches
Guilloches are reminiscent of the shapes you may have made as a child with your Spirograph. As you started drawing with your pen carefully clicked into this gear-based toy, you couldn’t really see where the design was headed, but by the time you had gone around the entire shape, it was a really interesting medallion you could never have thought up or drawn by hand. I used to play with mine for hours, with the brutal pen pressure only a 10-year-old can inflict. There are permanent Spirograph designs etched into my parents’ dining room table.