Classic

 I only watched a bit of this PBS Masterpiece episode, but the beginning was interesting.

The scene shifted around quickly and I had some difficulty identifying the camera.  When she advanced the film and cocked the shutter with that lever, though, it was clearly revealed as a Zeiss Ikon Tenax I.

From Wikipedia:

The Tenax I is a 24x24 mm fixed lens camera by Zeiss Ikon launched in 1939.

The Tenax I was actually launched after the Tenax II. Like the Tenax II, it is a 24×24mm square-format camera taking over 50 exposures on a standard 135 film (35 mm), with a rapid-advance lever next to the lens. But it is a much simpler camera, with a completely different body, no rangefinder, a simple folding viewfinder on the top plate, and a Compur leaf shutter to 1/300". Most of them are equipped with a Zeiss Novar 3.5 cm f/3.5 lens. A smaller number have a Carl Zeiss Jena 3.5 cm f/2.8 Tessar.

Production began in 1938, and it was nearly halted in 1941. There was limited production during the rest of the war.