I think if you tried to put it together, you'd find out as you tried to screw it together.

For post 1984 models to 1995, the side of the expansion valve with two small holes (not the holes the lines fit into) faces the evaporator lines. The face with three small holes faces the lines to the compressor. If you try it the other way, there is no way to secure the locking plate on the lines to engine side.

Hope that helps- those are the only MB cars I know anything about!