A system includes an identification circuit, a grid antenna, a receiver, and a processor. The identification circuit includes resonant circuits formed on a substrate within a perimeter. Identification may be based on a quantity or physical arrangement of detected resonant circuits within the perimeter. One resonant circuit provides a reference signal. Any resonant circuit may be tuned in accordance with the reference signal by the addition or subtraction of reactance formed on the substrate. A capacitance of a first group of capacitors located outside a turn of an inductor is roughly equal to a capacitance of a second group of capacitors located inside the turn. Any resonant circuit may also be tuned by affixing a resonance modifying element, for example a sticker, to the identification circuit. The grid antenna provides antenna field patterns, one for each cell location. The receiver communicates with the identification circuit via the grid antenna. The processor controls the receiver according to a method including: (a) detecting a first signal at a first grid location; (b) determining an offset as a difference between a frequency of the first signal and a predetermined frequency; (c) detecting a second signal at a second grid location; (d) determining an identification in accordance with the first and second locations, the second signal, the offset determined in step (b), and any offset accomplished by a sticker; and (e) determining an orientation in accordance with the first and second grid locations.