I ended up with three of these nice new variacs (well, really they are "powerstat") since they are made by superior electric - I've seen these used to adjust the input voltage to the control circuitry to compensate for line voltage variations, among other things. Some of you folks have talked of this situation, so maybe this will be useful (and yes, it's metal - copper and iron, so it's even on topic, no?)
here's the link
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