German optics covers a wide range of things, from the scopes on sniper rifles to the optic on the FG 42.
Generally not internally adjustable, the adjustment was in the mount. As mentioned, nitrogen filling didn't come until later.
I once found a scope for the FG42 on a "junk" table at a gunshow, for $5
Cute little thing, square where you'd think it should be round, reticle was 3 heavy posts (bottom and sides) it had some damage, part of the field of view had what looked like thick "ropes" of hair but the undamaged part of the view was decently clear.
External adjustment (in the mount) scopes were common in military use in that era, Shooters were generally trained to use "Kentucky windage" (hold off) for drop and wind, rather than adjust the scope (or mount). They guys who could do that well became snipers.
Scopes without internal adjustments were more durable than ones with internal adjustment, in that era and that was preferred by militaries over ease of adjustment.