Metallicity distributions of the GSE (top panel) and Thamnos (bottom panel) coming from neutral Fe lines. The median metallicity of the distributions and the standard deviation are also reported in each panel. For GSE we report the MDF derived in this work (green) alongside the stacked MDF using also stars from Paper I (dark green). We note that the shift in metallicity we find between the two samples in GSE might be due to a gradient in the progenitor reflected by the position of its stars in the E-L_z plane (see discussion in the text).