An insulative substrate web having a conductive surface on a first face is printed and etched to provide a repetitive conductive circuit pattern. In one form of the invention, the pattern defines a first conductive area serving as a first capacitor plate, and an inductor connected thereto; conductive material is applied to the second face of the web to define a second conductive area aligned with the first conductive area and serving as a second plate of the capacitor, and a conductive strip connecting the second conductive area to the other end of the inductor. In another form of the invention, the pattern defines first and second conductive areas connected by an inductor; the web is folded so that the conductive areas are aligned to form respective plates of a capacitor. The web may form the capacitor dielectric, or an insulative layer may be inserted for this purpose; and the web is sealed to fix the capacitance. The web is severed to provide individual planar resonant tags.