The Century of Progress World's Fair - held in Chicago in 1933 and again in 1934 - was among the most successful World's Fairs of all time, actually turning a profit. It was also the launch-pad for Tru Vue's toy-format 3D filmstrip system, which documented the Fair over 8 different filmstrips. This is the first one.
With most sets of stereographic images, you can get a sense of what's going on from the captions, action, provenance - all sorts of things. Here, I'm more or less at a loss - but the stereoviews are pretty darn cool!
An amateur set of contemporary modern ruins photography of Reims, at and around the bombed-then-burned-out Cathedral, and probably taken well before the end of the Great War, shows 12 views from a very talented photographer, documenting the damage to a beautiful city and its centerpiece.
An amateur set containing 7 views from the Great War: 3 of an ambulance convoy leaving to pick up the wounded of Champagne, 3 of a convoy at Saint-Mesmes, and one of soldiers camped in a small village (probably the latter).
Two glass plate negatives from the 1937 Exposition Internationale in Paris, taken from roughly the same position, give a window into the history of the Expo, as well as some of the underlying tensions that were coming to a boil in advance of the Second World War.
4 "digital prints" from negatives of life in the camp of the 36th Artillery Regiment stationed in Saint Airy Forest at Verdun in January 1918 show snowbound soldiers near one's shelter - as well as a peek into the shelter itself!
Marketed as the collection of a French Artillery Sergeant's personal photography before, during, and after the Great War, I was sold a disparate collection of mostly-junk by an eBayer who didn't know what he was talking about. Here's the story, and one of the few slides that likely had anything to do with the Great War.