Detailed intensity-energy LEED spectra from the clean surface (2*1) structures of Si (100) surfaces are presented from three independent and previously unpublished experimental studies at three different laboratories. An extensive range of data is presented and some detailed comparisons of the different data are presented. These comparisons show clearly both the reliable and unreliable aspects of experimental LEED data. The data presented provide an extensive basis for proper interpretations of the structure of this surface.