blloyd7, here's the photo of the OM603 camshaft marks (note they are NOT lined up in the photo). The factory service manuals specify replacement on OM61x chains at 5 degrees stretch or more, and OM60x engines at 4 degrees stretch or more. OM60x engines have NO provision for offset keys/pins. Here's two PDF's related to the OM60x timing chains:
http://www.meimann.com/docs/mercedes/OM60x_Timing_Chain_TSB.pdf
http://www.meimann.com/docs/mercedes/OM60x_Timing_Chain.pdf
