Histogram of the metallicity residual [Fe/H]_SP,cal–[Fe/H]_RVS,cal for two samples. The gray histogram shows the DR1 VMP candidate pool, defined as all DR1 sources with either [Fe/H]_SP,cal < −2 or [Fe/H]_RVS,cal < −2, while the blue histogram shows the final intersected VMP sample selected in this work. The final sample displays a much narrower distribution strongly peaked near zero, in contrast to the broad residuals of the DR1 candidate pool.