I've found the exact model of the Mercedes with the MP5: Mercedes-Benz W126-420 SEL armored police car
flickr.com/photos/govert1970/8708699713/in/photostream:
From the flickr URL above, click 4 photos back and you'll see the same picture as in the Johnny's post. Today, the car is in a museum: polizeioldtimer.de/oldtimerseiten/db_126%20gepanzert.htm. It was made in 1991.