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That coil may use litz wire. Litz wire is like stranded wire, except each strand is insulated. Reduces skin effect at RF. What I'm leading up to, is maybe one or two of several strands are broken, and that would result in a higher resistance reading. It would reduce the Q of the circuit, but that might not be worth worrying about, it could be a feature even, making for wider bandwidth of detected audio signal.
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