of arbitrary length which strip is conversion coated with a complex compound coating approximately 2000 u00e5 thick having shallow peaks and valleys of a depth which is less than the thickness of the coating the depth of valleys the dimensions of the peaks and the precise structures of the crystals and therefore the density of the coating will depend upon the conditions used for producing the coating since there is no convenient way of measuring the density of the coating formed suffice to state that the true density of the oxide formed is in the range from about 2 5 3 2 gm cm 3 the conversion coated strip is then coated with a fluoropolymer coating approximately 0 5 mil thick a portion the near portion in the figure of the strip 20 has a thermoplastic strip 22 adhesively bonded to it after the matrix fluoropolymer coating is treated with a corona discharge and an adhesive applied to the treated surface no adhesive is applied to the far and near portions 24 and 26 of the strip 20 because it is to be left bare showing the highly reflective surface of the strip referring to fig2 there is shown an elevational view of another strip 30 of arbitrary length about 20 mils thick having a generally right angular profile including a laminar horizontal.