Centrifugal ball mill, Planetary, Adjustable speed/time, S100, Retsch . This is a used centrifugal ball mill made by Retsch, model S100. We powered the mill up and the controls all work properly and it sounded good. The knob. Planetary Ball Mills PM 100, PM 200 and PM 400 - VERKON. It can only be opened when the mill is at a complete standstill.