Left: sum of the lower-left panels of Figs. 5 and 6. All ages are represented by the dots. The colour indicates the metallicity as before. The black box displays the limits from J23, and the red grid shows the bins used for the χ² test (Sect. 4.3). Right: same as the left but for randomly sampled clusters. The grey data points represent the observational data from J23 (see their Fig. 4 for error bars, which are omitted here for clarity).