Left-hand panel: Gaia CMD for the globular cluster NGC 5272. Red symbols indicate the giants for which a metallicity estimate was derived by means of the synthetic Strömgren photometry. Right-hand panel: metallicity distribution inferred from the synthetic m₀ index for the selected stars. The vertical red line marks the 2.5σ-clipped mean value of [Fe/H] = −1.59 (σ = 0.14). The cluster spectroscopic metallicity as quoted in Carretta et al. (2009) is [Fe/H] = −1.50 ± 0.05.