Under dash oil. But, not from oil pressure line.
 

1980 300D (non-turbo)
290K+ miles
Original ignition switch assembly.
What does it mean when you find oil dripping out of the ignition switch assembly in the dash ?
Is it time for a vacuum pump rebuild ? Lately, I’ve also had times (intermittent) when the engine took a few second to shut down after I turned the key off. Related ? Any special tools needed to fix/clean-up ?
Thanks for any advise.

No, not the vacuum pump.

The diaphram in your shutoff device is torn, allowing engine oil to be sucked into the key switch. Look through the first couple pages of threads in Diesel Discussion, as replacement has been discussed with the past 4 days.

Edit: my fingers did the walking for you. ;) The thread is here. Be sure to read the threads mentioned in the links there about the dangers of replacing the shutoff valve.

Thanks Rick
 

Thanks Rick. And for the quick reply as well. I got in just under the wire for ordering a new S/O Valve that will be here Monday.
I aslo have a profesional MB mechanic that will install it for me.
He said something about if it goes in wrong, I could have some problems with racing up the rpms and it not wanting to shut off. I figure he can have at it. I know he's done quite a few.

I've also got a Vacuum pump repair kit coming just for grins. I know I'm running the original pump, so I think I'll put a kit in it before it gives up on me while I'm some place I'd rather it not.

Now - If I could just get the windows back in proper order.