I was recently loaned a set of stereopticon cards from the Great War period.
Among them were some nice views of helmets.
Close up of French infantryman serving a machinegun.
French mounted troops wearing the m.15.
French artillerymen.
French soldier with a captured German flamethrower.
Finally, this shot, which is a gem. Members of the US 89th Division
with divisional insignia very uniformly painted on their helmets.
Sometimes seeing double is a good thing.