DavidF: The holes you pointed hold a pin to indicate the timing of the engine on the vibration damper. I don't see the pin on the picture, so i'm assuming it was knocked out by the damper.
As 97 SL320 pointed out, the damper has rubber in it. This rubber can get deteriorated by oil.
So, in my opinion, this is what's happened:

-Your engine developed an oil leak;
-The oil makes it to the damper;
-The damper rubber deteriorates;
-You take it to a high speed (high damper rpm) drive;
-Damper fails, taking out the timing pin (the holes you pointed).

You should do something about that oil leak before fixing the damper, though.