For the older style MagCs, first you must remove the spanner type retaining ring completely. Then remove the switch cover boot w/ needle nose pliers, using a 2mm allen key (long side), loosen the set screw that is deep down in the switch. With the switch in the "on" position push the switch assy. out the front. Sometimes if the switch seems stuck, with the allen key still in the switch I move it side to side to break it loose.
For the newer style, with the switch boot removed & the switch in the "on" position, loosen the allen and just slide the switch assy. out the back the same way you would disassemble a MagD.
I have a Mag3C and had a Mag2C that I modded for someone that both have the Mag logo on the switch boot. Both have a "C" in front of the serial # indicating the newer style MagCs. As far as D's I have never seen the Mag logo on the switch boot on any of them neither have I seen any MagDs w/ no letter "D" in front of the serial being sold in the past few years. All MagD's I've seen all have "D" in front of serial #.