Well, MB clearly made a design change with the '96 year.
Your lens is in two pieces... one toward the windshield that surrounds the switch and another that covers the main bulb.
My W140 has the lens all in one piece. Checked a '98 today and its one piece also.
When I pop the lens off, I can see where the grey plastic housing is molded to have a lever there, but there isn't any...
So, they obviously got rid of the levers (whatever they were supposed to do) and went to a one piece lens.

My dome light stays on for 20-30 seconds and then just shuts off... no fade.

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KenP

1996 S500 W140 Coupe