RGB stars shown in the lightest gray cross symbols, as well as those RGB stars that were selected for the MDFs, shown with the darker gray circled-cross symbols. The fiducial derived using all the RGB stars, RGB_ALL, is outlined with the red open circles, while the fiducial derived using those RGB stars that were selected to construct the MDFs, RGB_MDF, is outlined with the black asterisks. The red dotted line corresponds to the Dartmouth 12.5 Gyr isochrone that best matches the RGB_MDF fiducial, while the black solid line corresponds to the one that best matches the RGB_MDF fiducial. From left to right and from top to bottom panels, the red dotted lines correspond to a metallicity of −1.55 dex, −1.75 dex, −1.85 dex, −1.65 dex, and −1.9 dex, respectively, while the black solid lines to a metallicity of −1.65 dex, −1.75 dex, −2 dex, −1.75 dex, and −2.1 dex, respectively.