Gentlemen, I just ran across this thread while looking for a Euro lens replacement for the "new" 1994 E320 I just purchased for my wife. The one on the right headlight is cracked.
While the primary mechanism for aiming the headlights is as Duck Muck describes, the actual lens "design" does have an effect on the beam pattern. The lens optics can "shape" the beam in width and height, while the reflector governs where the beam center is aimed. My suspicion is that the Euro and NA lens optics are different, so each lens "design" produces two separate and distinct beam patterns. Fresnel lenses do exactly that, so I am assuming these designs use that concept to achieve the desired beam shape.
My $.02.
