I think what happened at some point is that your ignition lock got "sticky" and a replacement barrel was sourced from a parts carts, and perhaps the driver's door lock was changed at the same time.
My situation was this:
- The ignition barrel had been slightly "sticky". (If this happens, it's a warning sign! First off, I'd order a new key from M-B and see if it fixes the problem. If it doesn't, you need to change the ignition barrel out, because if it seizes, then it becomes an absolute nightmare to change over. The key needs to be in position two to slot in the release tool (basically a straight piece of wire) to be able to pull the barrel.)
- The little door on the driver's side door lock had fallen off. This would allow dirt and water to enter the lock barrel directly, a sure way to accelerate lock and key wear and ultimately lock death. (This little part cannot be replaced on its own. Also, the barrel cannot be replaced on its own, the lock is integral to the door handle, so has to be changed as a unit.)
So, in my case, I was forced to do something as I had the double whammy mentioned above. I knew it would just be a matter of time before the locks got totally stuck, and I would be stranded.
New lock sets are a thing of the past. I managed to buy one of the last W116 lock sets available from Fellenbach (M-B Germany classic parts) for a non-central locking car. The central locking set in NLA. The parts guy and I thought in our naivety that we could simply remove the "hook" on the boot lock, and screw the central locking componentry onto the back of the new boot lock, but it's not a fit. I might have to send it off to Belgium to the lock man to have the tangs in the barrel replaced. So, I do have one key essentially to work everything when I get the boot barrel re-keyed, but it is also not the same lock number as on my data card.
To those of you who can live with more than one key, the news is equally as bad if your ignition barrel goes. I know insofar as the newer key types go (like the one Lucasz pictured - square profile with the pattern cut into the key as opposed to the "teeth" being on the edge) the ignition barrel is NLA. I do not know what M-B expect one to do when your ignition barrel is about to or has seized, as they don't actually give an alternative ignition barrel. I found this very strange, as this key type was used in late W116's, R107's and W201's. Now with 2 door M-B cars being quite so popular you would have thought M-B would pull themselves together and ask Huff locks to do a new production run...
So, Rumb, I'm afraid your lock issues are going to be a bit of a struggle. Lucky for you and me, even if we did nothing to our current lock sets, we already have that wonderful anti-theft device installed in our cars: the fuel consumption...