Assistance IDing this temp sensor

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there's what I'm guessing is a temperature sensitive switch, but I don't have a proper name for it.  What would this device be called?  From diging through the Mouser catalog I came across thermoresistors that sound like they could be it, but from what I'm reading they don't function like this does.  Any help IDing this part?

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I think thermo-switch could be a good name