That push/pull knob is (I believe) the suspension up lock. There is a Type 100 forum that is for owners of these special cars. I do hope it is in well maintained condition and not a 'fixer-upper'. MBZ has, in the past year, raised repair parts for all non-current cars by astronomical amounts. Major parts that were $1000 are now $3000+. Minor parts that were $3 and now $12, etc.