Until recently, MB used to provide with each german built car at least, an exploded little parts book, which showed all the separate parts in the car.
It was about the same size as the owners manual.
It showed the parts grouping, which meant you could contact the MB dealer parts man, and when you gave him the group number, and the item on that page, he could convert it to a proper part number.
It was a good idea, as it took away, any mistakes.
In otherwords, can I have that little gizmo, that goes onto the what do you call it.
I must find out when benz stopped producing them, because they are not vailable for ML's.