The brushs wear down and that takes way from the output of the alt efficiency...do an output test..or, just change the reguiator if you see the brushes are worn down from NORMAL wear..
..........2 screws.
Now that we have the correct model/yr, here is the corect part..
http://catalog.peachparts.com/RenderScriptTemplate.epc?_cmd=epccat_VehicleAAA&cookieID=2FG17RJ3A2FH0ROLMO&yearid=1995%40%401995&makeid=MB%40%40MB%40%40X&modelid=E%2D420%2D001%40%40E+420+Sedan&catid=F%40%40Engine+Electrical&mode=PA&subcatid=F4010@@Voltage+Regulator&source=www.peachparts.com&clientid=catalog.mercedesshop
..or , you can wait til the alternator goes from the bad brushes eating the rotor and replace the whole thing for 5 times as much as the regulator..