Some Brass parts inside are heavily corroded and so it seems likely that it was moist or even wet (with hydrofluoric acid or something similar -.-). I hope that the PCB and the switches are ok (the liquid shield is in good condition but the brass underneath is corroded around every switch what makes me worry - the switches are all pressable and nothing is stuck though). Bevor having a look at them i want/need to remove the Keycaps (sturdy little bastards , one need a looooooooot of patience to remove them... will take some hours, literally).
From the outside (case) it is besides this maaaaaaaaaaassive amount of dirt it is ok aside from some minor imperfections (some scratches at one edge of this black led holder thing at the top, some cracks in the painting, corroded spring and axis from the plastic-cap of the manual and keys are more or less shiny).
Here are the first scary pictures: