Constraining power of various features in terms of measuring the stellar metallicity of ID53. The vertical grey bands show wavelength regions that are not included in our analysis due to contamination from interstellar absorption or nebular emission (at λ₀ < 1600 Å) or because they are not covered by the MUSE data (λ₀ > 1600 Å). The coloured lines show the best-fit burst model for each stellar metallicity relative to the lowest-metallicity model. The models are fit to the MUSE data only, ignoring wavelengths with features from interstellar lines or nebular emission. The horizontal grey band illustrates the typical S/N of our data. We illustrate the locations of the N V, O V, Si IV, and C IV P Cygni features in red.