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Now rack your brain for Class 2 (double Insulated...no earth wire)

Non contact voltage detector pen. These can usually detect even as low as 100v through several cm of insulation/appliance casing. (A double pole changeover switch securely mounted to a short extension cord or 'power strip', labelled "FOR TEST USE ONLY" and reversing phase/neutral is very useful for this kind of test, to compare results, I have one I made years ago, with a 15 amp toggle switch mounted in a 20mm conduit knockout on a double outlet. It's also been added to with a momentary 15amp pushbutton 'start' type switch, to prevent any but momentary use.)

If the class II appliance is metal cased, (unusual) the reaction will usually be unequivocal, if it's plastic (more usual) you'll have to go poking around with the detector pen, but you can usually tell which line is switched.

As Paul said, a reversed phase/neutral is no big deal in an appliance that's class II anyway, but it's nice to get it 'right' [Linked Image]