Hi David, It looks as if your helmet is a light-weight HGU-55/P with integrated chin-and-nape strap and with a visor housing much like the one used on the HGU-55/G. Both your visors are like the ones used on the HGU-26/P with side-actuated lock knobs.
An original HGU-55/G made to German specs (G for Germany) would have had a British type of chin strap with the same locking system as the German Gueneau 316G helmet. Further, the visor has a slot for a visor lock screw in the left side.
I am not quite sure who took these pictures so I will remove them from the internet again in a short while.
Cheers, Bluelight
