According to Google, the 75000 was a phototube, which is an electronic device.
It would have been used in a projector to read the audio track on the film.
That makes sense for Kodak.
It should have a black Bakelite base with a few metal pins sticking out. That's the bottom.
Above that is a glass envelope that has a metal cap on its top.
The sensor is a curved metal plate inside the glass envelope.