Comparison of the disentangled spectrum of the stripped B star with stellar model atmospheres of varying hydrogen content. The panels show wavelength regions around the Balmer Hδ, He I 4120 Å and Si II 4128,4131 Å lines (left to right). The disentangled spectrum is shown in grey, and the fiducial best-fit model (T_eff, B = 13.5 kK, logg_B = 2.25, flux ratio 60%) with hydrogen mass fraction X = 0.3 in black. The models vary X while keeping other parameters fixed.