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Yes I also recall seeing them in Clarks but unused

I remember seeing and using the one from 1996 in my early childhood as displayed in this article:

Not sure if these actually used X-rays but it'd be interesting to find out if they did.

EDIT: In hindsight, I really don't think the type I remember used X-rays.

ANOTHER EDIT: Looks like this is the company that made the ones I can remember: http://sensatech.com/applications/index.html