I do know that Mercedes cars should have Becker radios.
When I was a little boy, my dad's Volvo P1800S had a Blaupunkt Köln. I remember looking at that fascinating little pointer travelling across the face, seeking radio stations.
I wanted to have a similar Blaupunkt with automatic tuning even though there are Beckers out there with the same feature.
I bought two Blaupunkt Kölns from ebay. They were both sold as inoperative. To my surprise, they both started to work after cleaning and lubricating the tuning mechanism.
Here is a picture of my basket case Blaupunkts (two Kölns and one Frankfurt)
...and this is how one looked after cleaning. I bought new knobs and some other small parts to it as well as a new speaker and an automatic Hirschmann antenna.