Charles,
A good way to find this information out yourself is to contact your local INDEPENDENT BMW, Mercedes, and Porsche REPAIR facilities, and ask them for recommendations. If you can't find these, contact the local sections of the BMWCCA, Porsche Club (I think there are several) and MBCA, and talk to the officers of these clubs. They'll tell you the well-respected repair facilities, and might even have the body shop recommendations.
If you were to do that around here in Detroit, a very short list of body shops would arise; I'm certain the same would happen in Baltimore.
That being said, Bob Platz of Precision Autoworks in Camden, NJ has restored many fine Mercedes; and is well respected among the Gull-Wing and 190SL groups. I've also seen his work and it is wonderful. Camden should be close enough to Baltimore. If his shop can't help you, he can certainly point you in the right direction.
Bob Platz
Precision Auto Works
2202 Federal St
Camden, NJ 08105
(856) 966-0080
Good Luck.
Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored