Lost key!!

Something doesn't sound right here. My 300SD 1980 has a master key and a secondary/valet key. The master unlocks everything, the sec/valet unlocks only the doors and ignition. That makes sense, as if you have the car parked, you may not want them to have access to the trunk and glove box.

I can't imagine why a car would come with a second key that only works the ignition, as this sounds useless. Are you sure you have the right key? In any case, you can open the vacuum locks by pulling up manually on the drivers button, though it takes some force, and hooking it and doing that may not be possible. A dealer should be able to make a new key from the vehicle information.

Sounds like your ignition tumbler went bad and someone replaced it with a generic?

For a few dollars more, they could have ordered the correct one with the matching key....

Go to your MB dealer and order a new key per your vin number. It should open the doors. If it does, then order a new ignition tumbler per your vin number and you will have one key for all. You will have 2 new keys, the one you ordered for the doors and the one that comes with the tumbler.

when you join us in the 21 century you'll learn that things have changed. Since the late '90s MB has been using electronic keys with chips in them that have to be used in the ignition and they have little xmiters that open and lock the car.