Oil leak where stereo fits in '80 300D 123?

[Fisherman]

I've been searching and searching a can't find the answer to this one.
I just picked up a 123 today for cheap. This means I will be asking a lot more questions over the next couple of days/weeks. But the immediate interesting thing that I found was when fitting a stereo into the slot under the acc controls I found what appears to be engine oil dripping from the ledge just above the stereo. Natural assumption would be that it is coming out of the acc controller and dripping down off this ledge.
I am going to take it apart tomorrow to see if I can pinpoint the leak but anybody have any ideas? Could this be a blown vacuum pump and oil has fed all the way up the vacuum feed line to the acc controls?
Any ideas would be helpful..
Thanks