I saw this on e-bay. Is it a battery heater? How would it work?

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The description says:

"Vintage Strato-Jet Hard Start Kit

I got this a box of old tools I purchased. I can honestly say I know nothing about this guy. I do know its old. That is all I can tell you. I can't tell you if it has been hooked up but it looks NOS. There is no way to check it so I'm selling it as-is. I really don't need it back so make sure it's what you need. It's in need of a home to display or use. Up to you. It is what it is. As-Is."

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