No Master Code as that would not be very secure for such an upmarket car.
Mercedes do not make radios .They only affix their badge onto radios made by the large manufacturers (ALPINE , BECKER etc)...... so in order to attempt to calculate your code , please quote your radio MAKE+MODEL plus ALL the NUMBERS+LETTERS on ANY LABELS , BARCODES or STAMPED IN THE METAL CASING
Also quote the number of station Preset Buttons on the front