That looks really clean, the one score mark on the tapered part shows it has not been ****ted with, as people rotate the thing clockwise to get more fuel at lower rpms, this then leaves another score mark as evidence.
It should be dry in there, I have never personally seen anything apart from grease and in one case water under there, but so long as its not peeing out I would not be concerned, if you notice on the back of the pump there is a rubber nipple, this is the breather for the space underneath the diaphragm, this is also where water can get into the pump if car is used for deep water crossings etc.
Might be worth letting the thing idle, and one at a time crack of an injector and see how much the rpms drop, do this on all four lines, and if they all have roughly the same effect you may be looking at the inj pump.