I've been having a really good close look at this Kaufman Posographe.
Printing off the pictures as A4 and then googling some of the French into English helped a lot
From a photographic point of view, it calculates exposure from Month, Time of day, Scene, weather and colour & lighting of the subject. Interior views use colour of light and colour of walls, I think (I haven't translated that bit, yet) and the 'zones' are the distance from the window.
There seems to be an emphasis on colour presumably because this would have made a big different in the days of 'ordinary' and 'orthochromatic' emulsions.
One thing that is missing is film speed! This is accounted for by the output display unit (the oblong brass widget) having four pointers on it. these are designated Ordinary, rapid, extra rapid and ultra rapid. I think they refer to specific plates and the spacing between them isn't even. They could be the equivalent of something like 2, 8,16,32 ISO, maybe? (Would Ultra Rapid have reached ISO 32 in the 1920?)
It seems to be it is a pretty comprehensive calculator that takes into account most factors and I reckon would have worked well, with the four types of plates it was intended for in the 1920s.