So, back over Thanksgiving I bought a 1982 Mercedes 300D Turbo Diesel. The car came with three keys. A square head key that fits the ignition, a rounded head key that fits the doors and trunk and a valet key that fits the ignition. I went to the dealer today to order additional keys. The dealer told me that I will be receiving one key.... He did not know which key.... In looking at the square head and round head keys that I have, I do not see how one key could be cut to operate the ignition and the door/trunk locks. I have also noticed that none of my keys will lock the glove box.

What key(s) should I have? Is it normal to have an ignition key and a door/trunk key or should one key do it all? I'm thinking that maybe my glove box door is not original so the keys do not work? If so, how could I obtain a lock for the glove box that would work with one of my keys?

 

Assuming it is an original the Square headed key opens all locks.
The round one only opens some of the locks.

If someone has installed a generic Ignition Switch Tumbler that can add an extra Key.

 

So, it would seem as though my ignition switch was replaced at some point in the past.... Is it possible to have a "factory" ignition switch installed so that one key would operate all the locks as intended? Can a dealer still do that? What about an independent shop?

 

If you go to the Dealership with your current Car Regestration (make sure the regestration VIN Number matches the actual VIN number on the left side of the Drivers Side front Window; US models). You will have to wait for it but the will get you and Ignition Lock Tumbler and for sure one key.
You may get more Keys with it but I cannot remember exactly what others have said concering how many Keys come with the Tumbler.
Anyway they will match that locks that came with your Car when it left the Factory.

If you have more than one Mercedes Dealership in your area I would call and ask them the details and also the price. The price because some Dealerships charge more than others.

Also if you are inclined to do so; if you become a Mercedes Club of (North?) America member you can get a discount on parts bought at the Dealership. How much of a discount depends on the Dealer.