Had the same problem with my 84 300D--a key for the ignition and another key for doors and trunk. Thanks to info in previous threads, I went to local MB dealer and had a new ignition tumbler made. You will need the VIN number and proof of ownership. It takes about 3-5 days to receive the new tumbler and master key, and locks and ignition will match.. It only took me 10 minutes to replace the tumbler(there are threads that explain how to do this) . The cost was less than $50, but for me, it was worth the cost to have one key for the ignition and doors.