Up for sale as a nice Becker radio Amplifier unit.  This has the "optional" line-out box.  001 820 92 89   /   A 001 820 96 89 / These are located in the trunk of cars that are equipped with these units.    Worked when removed, we had upgraded the sound system in a 1995 E420.  Has sat in the garage for about 6 years now, and has not been re-tested since removal.  It's a bit dusty.  It should still work, plug & play- I will give a 30 day functionality warranty on this unit!  Just check your original part number before you buy to be sure it is right for your car.  These things used to cost over $600 remanufactured from Mercedes back when these cars were still all over the place.  Listed much cheaper here...