Mercedes issues a basic oil change booklet with each car sale. The dealer stamps it off or whoever does the oil change does. They also date it with the milage the oil was changed at. This booklet is good up to about 120 thousand or so.
Needless to say if it is not in the dash forget the ideal of authentic milage. These cars can still look pretty good with 250k or more on them. If you desire a good example why not connect with the mercedes benz owners club. Also the price should be lower than what this guy is quoting. Who really wants to buy a car from a used car salesman anyways?