Some more progress...I will probably change back to wood for further experiments. The engraving bit does not last very long in that brass alloy, in spite of very conservative feed and depth of cut.
The text has nothing to do with the guilloche and is more a test of how much detail I can do with my machine. It is only 0.04" tall and barely readable. At that size it would need a clearer font and probably should better be engraved at constant depth instead of Vcarved.