As far as I know, Mercedes-Benz dealers have never had external "key readers". There is some key data that is displayed in the DAS and Xentry when passing through the EZS or if you have the CANalyzer tool to read certain CAN messages sent through the drive authorization system. The CANalyzer tool is generally quite advanced and most technicians don't know how to use it or don't need it.
Most of the information provided is correct in the sense that to check the vehicle's mileage you need to go into several control units. If you suspect that mileage readings are being falsified, do not rely solely on data from one control module. You will be very surprised to find out which control units have any mileage data, so you just need to use...