The proper method calls for checking valve lift with a dial gauge. You can eyeball it by lining up the cam mark with the cam bearin tower mark and reading the difference between 0-degrees on the crank pulley and the TDC mark next to the pulley on the timing chain cover. <5 degress ~ leave it alone, >5 degrees ~ keep an eye on it or change it now if it's the original chain in a 300D 2.5. Might only be certain years of the 300D 2.5 that has iffy chains.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD