I just realized that's a Wacom board... and sure enough, here's mine.pic.twitter.com/valXyUtYnp
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Maybe it's insulation for the *bottom* side —mine's on a metal plate, though there's an insulator layer— and they just do both?
Incidentally, how old is yours? Mine's an ancient Graphire2, interesting they're still using a largely identical circuit design.
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