CMD for stars within 1.5′ from the centre of BH176 (D11; small grey dots). Black open squares indicate the objects observed spectroscopically. Black filled squares show the RC and RGB stars selected according to our criteria to produce the co-added spectra. Alpha-element-enhanced ([α/Fe] = 0.3) isochrones computed from the Victoria-Regina stellar models of VandenBerg et al. (2006) are over-plotted: (from top to bottom) [Fe/H] = −0.1 dex and Age = 6 Gyr, 7 Gyr (red in the electronic version), 8 Gyr; [Fe/H] = 0.0 dex, Age = 7 Gyr (cyan in the electronic version).