I agree with the idea that they were made to develop glass plates, each tank with different chemicals. Probably 1920s.
Unfortunately, I don't think they are very valuable: this kind of tanks are relatively common (but, truth to be told, usually not in kits of 5 tanks), and yours should be restored before putting into use (if possible at all) and in any event looks like at least a good clean could help looking better for display.
However, I'm no expert, maybe they are some special kind or made by some famous factory, but I doubt it.
I'll be looking forward to what the people more familiar with these devices has to say :-D