It's a minor update and changes are mostly from a manufacturing point of view; circuit board enhacements mainly.
Emitters are still Rebel 100, but these I'm told are now 15% up on the light output a year ago which is where the current S7+ output figures date from. The latest LEDs also have a lower forward voltage so run time will be slightly longer.
If you've taken the back off your Sten (cleaning the switch for example) then if the cable is epoxied in it is a C/D/E. To check exactly remove the front window and the lenses and you'll see a sticker in the form S7x0000, x will either be C, D, E or F.
Dismantle over a tray or something incase the ball bearing or detent o-ring vanish!
my orders are to sit here and watch the world go by