Gaia colour-magnitude diagram of all the C-19 members studied spectroscopically. The absolute magnitudes are shown for two possible distances: 18 kpc (blue), and 20.9 kpc (black). The three non-member stars are highlighted in light grey (18 kpc) and grey (20.9 kpc). For comparison, three BASTI α-enhanced isochrones (Pietrinferni et al. 2021) of [Fe/H]= −3.2 of 14.20 Ga (red), 12.80 Ga (cyan), and 11.90 Ga (magenta) are shown.