Different trends observed for low-load Vickers hardness are due to visual perception problems of operators of where indent tips are, not a material problem. In 1925 in the UK, Smith and Sandland developed an indentation test that used a square-based pyramidal-shaped indenter made of diamond. The test was developed because the Brinell test (introduced in 1900), which (until recently) used a round hardened steel ball indenter, could not test steels harder than ～450 HB (～48 HRC). They chose this shape with an angle of 136° between opposite faces to obtain hardness numbers that would be as close as possible to Brinell hardness numbers for the same specimens over the usable Brinell range. This made the Vickers test easy to adopt, and it rapidly gained acceptance. The Vickers test has the great advantage of one hardness scale being used to test all materials, unlike the 30 different Rockwell test scales, each yielding numbers between ～20 and ～100.
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