You get someone to read it with the diagnostic computer.

As long as you don't want a replacement key or the original owners haven't used up all 8 keys that were possible the dealer should get you a key that has never been issued. There was 3 or 4 original keys including wallet versions. MB should have recorded the last additional key purchased.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician