Abstract: A presensitized offset printing plate is identified by its reflected light as one of the known presensitized plates of different light reflective characteristics. White light is casted on a freshly introduced presensitized plate to be tested so as to measure the intensity of the reflected light from the surface of the photosensitive layer thereon in four color signals, which are a magenta signal, yellow signal, cyan signal and black-and-white signal. Then the reflected light is compared in each color signal with the reference data which are inherently determined with respect to known presensitized plates of different light reflective characteristics, whereby the tested presensitized plate is recognized or identified as one of the known presensitized plates. Said reference data, which are different with respect to the known plates, are stored in memory means.

Abstract: A method and apparatus for resharpening cutting tools having an edge of complex curve by electropolishing process, wherein after a protective film is formed on the non-polished surface of the edge of a cutting tool, the edge is immersed in an electrolytic solution and DC voltage is applied between the tool, which serves as an anode, and a cathode plate immersed in the solution to thereby polish the edge by dissolving.

Abstract: A blanket for offset printing comprises three layers, namely, a substrate, a rubber layer and an outer layer. The outer layer is formed by applying to the rubber layer an urethane type resin having aluminum powder mixed therein, and the aluminum powder produces an unevenness in the surface of the outer layer which controls the ink transferring ability of the blanket.