This part of ISO 6507 specifies a method of verification and calibration of testing machines and diagonal measuring system for determining Vickers hardness in accordance with ISO 6507-1. It specifies a direct verification method for checking the main functions of the machine operation, and an indirect method suitable for the overall checking of the machine. The indirect method may be used on its own for periodic routine checking of the machine in service. If a testing machine is also to be used for other methods of hardness testing, it shall be verified independently for each method. This part of ISO 6507 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.