At work, late in the previous century, I found something similar stuffed away in a corner. If was a three-phase version with one more stack of toroidal auto-transformer ganged with the other two on a common shaft, along with some sort of inductor in a black bakelite case on each one, purpose unknown. So I took the pieces apart and used them separately on lab furnaces, discarding the inductor (or whatever it was). A nice chunk of iron and copper, it was. I could barely lift a single auto-transformer from the stack. The stacked combo was more or less up for grabs when I found them, but my wife isn't as nice as Morticia: I would be dead meat if I had brought even
one of the stacks home.
Still... opportunities lost. <sigh>
Congratulations on your find, Bob!