I bought a 1979 300SD that came without a trunk key, so I took a drift and a heavy hammer (5 pounds?) and punched the cylinder into the trunk. Now I open my trunk with a screw driver. There is a little lever sticking down from the top. I jamb the screwdriver in at the 12:00 o'clock position and the little lever pushes back (the lever moves towards the front of the car) and the trunk opens. Sometimes I get it on the first try. Other times it takes a lot of fumbling around.