On/offroad package?
I own a 2008 model ML 350, with the optional off-road pack.
Quick way to check if ORP installed...should have diff lock dials (for rear & central diffs) and also the letters "LR" is printed on the off-road selection button.
If no "LR" printed = only basic off-road driving assist mode, which does NOT have low range.
The console looks a bit different on the 2013 model as you posted. Both diff locks and low range are present and that comes only with the ORP, which means this vehicle is definitely equipped with the off road package.
Regards an enjoy...
Diff lock dial to the right of low range button
If it is an Ml (or GLE) then it is probably unique to your market.
The W164 and W166 here were never available with an interaxle diff lock.!
They only came with the controls as shown in David Hartmams picture.



