It is a plastic "walnut" that is split into two halves and can be opened. In the walnut are two strips of old photographs of the Century of Progress (zoom in on the photos to see details). I'm not sure if the two strips used to be one strip, but I don't see how they could have been attached.
The first strip of photos has 15 photos. It is intact.
The second strip of photos has 20 photos. It is intact.
The "walnut" is about the size of a large walnut, so the photos are tiny.
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