Small 1939-40 viewer

.....Small plastic {of some kind}, viewer that came from the 1939-40 New York's World Fair.

Viewer contains a small loop of 16mm film, that shows {still pic.}, of various displays / pavilions from major companies.

Measuring ruler is 7" in length, to show item size.

I was given this item by someone returning from that '39-'40 Worlds Fair. I don't remember who was the "giver".

One holds the viewer up to a back light....and peeks in the viewer to see pic.