Technical Oil in 4x4 transfer box ?

[Hharbers]

I was looking at a spare transfer box of my 1987 4x4
Looks like there is a filler and drain plug.
Should there be oil in what needs changed at interval?
What kind of oil?
Cant find any information on it

 

[Hharbers]

Found smalle slotted openings in housing next to the bearing of input shaft to let gear oil in from gearbox.
Solved