@jpm It does indeed look haunted!

It's a head-scratcher. I've been looking at it and trying to figure-out how it works. My guess is that the creepage in each section was selected very carefully to give those not-quite-touching tracks a certain capacitance (and each one looks slightly different), so the whole thing acts as an LC circuit or a series of LC circuits.

With variable capacitors I've seen in old radios, it's a matter of rotating a bunch of metal plates to tune the resonant frequency. You just turn the knob until you hear that the radio receiver has landed on a radio station. But this circuit is hardwired. How you'd know or be able to calculate such a thing for predictable and reliable performance seems like magic.