This German helmet is the model 1A1 used by the airborne troops or Luftlandetruppen.
This type of helmet has been in use since 1961.
Notice the blue/green camouflage I think this has been done by an induvidual soldier. I haven't found any information yet telling this was officially used by Germany or Belgian Airborne troops.
I'm thinking about Belgian troops based on picture 4. One can clearly see the place where I think was the Belgian flag.
I found information showing this is a Belgian used 1A1 LL: An essential difference between the German and Belgian models is the small leather strap that turns the chin strap into a chin cup. The Belgians designated this helmet as the Model 71.
The helmet liner is dated September 1980 and made by, again, SW or Schubert Werke.
The Belgian paracommandos also used these helmets with a French style liner as shown in a previous articale: