First, I ssume you removed one of the hoses so we could see the device. I still think it is a thermal switch for vacuum advance. Mine had a number stamped in the flat on one of the hex faces. I pulled it out and put a plug in its place, cleaned it off and found numbers. Then I tok it to my sort of friendly MB dealer and bought a new one, tested its function with near frozen and near boiling water, and installed it. Be carefule of the vacuum tubes when removing and installing.

Incidentally, why are you certain a new one is required unless one of the tubes is broken?