This aluminum-tungsten dendrite specimen is used in evaluating the resolution and performance of SEM's. The dendritic structure formed on the surface has various spacings that can be used to evaluate the resolution at both low and high magnification and has a high secondary electron emission. An SEM micrograph is provided with each unit that locates the structure. It is nonmagnetic, vacuum clean, has no adverse reaction to an electron beam, and no surface preparation or coating is necessary.