[Fe/H] and [Cu/H] in this analysis using the VALD3 line list and in Ivanyuk et al. (2017) using the VALD2 line list (top panels). The same, but using the VALD3 linelist in both analyses (lower panels). The red error bars belong to the data of Ivanyuk et al. (2017), and the black bars belong to the present work. The linear fit to the data is shown by the solid line. The position of the equidistant values is indicated by the dotted line.