Abstract: A wafer construction which includes an expansive, generally flat plastic member formed with a spiral groove in which an elongated electrical conductor is held in the shape of a coil. The plastic member is also formed with a recess in which a capacitor is contained. The capacitor is connected to both ends of the conductor to form a resonant electrical circuit. A hardened steel reinforcing element is also embedded in the wafer around the wafer circuits to protect them against severing. A tack-like fastener element has a concave head which telescopes over a dome-like projection on the wafer to provide a tamper resistant fastening assembly when the tack shank is inserted into an opening in the wafer.