Comparison of the spectral types obtained from the visual comparison with metal-poor “templates” and spectral types derived from the spectral indices defined by Gizis (1997) and Lépine et al. (2007). Subdwarfs, extreme subdwarfs, and ultra-subdwarfs are marked as squares, circles, and triangles, respectively. Metal-poor dwarfs with discrepant spectral types derived from both classification methods (comparison with templates vs. spectral indices) are displayed with asterisks (e.g. sdM vs. esdM or usdM vs. esdM, etc.). Typical uncertainties on the spectral types derived from both methods are half a subclass.