how can i tell new and old version of 360 controllers apart?

i have a xbox 360 controller and would like to do the rapid fire mod. however i cant tell whether i have the new or old version of the controller( mod doesnt work on new version) i have the metal box/thing every 1 is saying is the crystal, but its on the backside of the circuit board. how can i tell if my controller is new or old version?

It has to be in the front not in the back. Thats a CG controller. (Common Ground) The one you can mod is the Matrix Controller which has the resistor or crystal in the front