Some of you may not know what the dead bolt is. W123 and the early w126 do not have the dead bolt. Since the lid is 1/8 open, I agree with Benzmac that the latch is clear but it is held up by a dead bolt. The dead bolt is located 2 or 3 inches to the left of the latch.
If it is the dead bolt that is causing the problem, I think, one can drill a small hole some where on top or behind the license plate and insert a pick or a small screw driver to move the dead bolt. Now, the problems are where exactly to drill and how to move the pick to unlock it. You will have to look at another 300SDL to find out. Maybe, after you look at another car, you decide this method is not doable. This is just my thought based on the methods used by locksmith opening safe and combination locks. I have never heard of any one using this method to open a trunk before. Dealer or locksmith may have other ways to open it. It is just my theory waiting to be tested (at your own risk). After it is successfully done, seal the small hole with proxy glue and touch up paint.
The fuel tank is behind the rear seat. I do not think it is possible to got into the trunk from there.
Wish you good luck.
[This message has been edited by be459 (edited 01-29-2000).]