Quite possible it was used as a series load bank. I use 2 x 100 watt lamps parallel in series with an appliance under test, especially for radio's, tapedecks and the like to have a limiter in case of a dead short at a faulty appliance. I take one lamp out depending upon VA rating of appliance under test. I like to see the porcelain fittings, a lot more durable then the plactic c%@p we get now these days.
The product of rotation, excitation and flux produces electricty.
