Hardness testing, as is true for any operation performed under ISO/IEC 17025, requires a meticulous approach.  It goes without saying that, apart from the sample preparation, the execution of the hardness test itself is decisive. With ISO/IEC 17043 accredited proficiency testing, you can examine your measuring and testing performance using the common methods, including the Vickers, Rockwell, and Brinell tests.  Apart from proving your competence, the proficiency test is also an aid to help you in your dealings with regulatory authorities and accreditation bodies.