closer in #59, make the knob the orange color and the area outside the concentric circles orange as you did the pink in # 55 It also seems that the black and grays in #55 have more contrast than the one in #59 which I prefer.
Nice job! You certainly know how to listen to what a client wants. I do have to say, there are a number of very good entries out there. Of all the ones that you have done, which one do you think works best?