Great to see this old stuff,
my guess is that it is probably 1920's.
I have to agree with the other comments that it is probably from a science class and used for showing students what a variable inductor does and a capacitor in series with an electrical lamp circuit.
What are the voltages from the lamps ?
110 Volts or different ?
It looks like there are 3 capacitors on top of each other in parallel. they may have been used as singles too to show the different brightnesses of the lamp with different cap. values.
The product of rotation, excitation and flux produces electricty.