This document specifies a method of verification and calibration of testing machines and diagonal measuring system for determining Vickers hardness in accordance with ISO 6507?1. A direct method of verification and calibration is specified for the testing machine@ indenter and the diagonal length measuring system. An indirect verification method using reference blocks is specified for the overall checking of the machine. If a testing machine is also to be used for other methods of hardness testing@ it shall be verified independently for each method. This document is also applicable to portable hardness testing machines but not applicable to hardness testing machines based on different measurement principles@ e.g. ultrasonic impedance method.