The main thing is the comfort of your body. A chair that is comfortable to sit on with an almost straight back, a microscope at such an altitude that you don 't have to bend your back or pull your neck like a turtle.
Based on the focus distance of the microscope, and the height of the engraving...
By definition, I don 't have a turntable. I found this forum and found out about the turntable recently.
Much after making two-wedge vise with a turntable and shift.