Échelle diagram of the very low metallicity RGB star KIC 4671239, with the stretched period τ modulo ΔΠ₁ on the x-axis and frequency on the y-axis. All dark symbols indicate dipole modes with a height above 5 times the local stellar background; their sizes depend on the mode height. When the azimuthal order can be automatically identified, triangles correspond to m = −1, squares to m = 0, diamonds to m = + 1. Light gray symbols correspond to unidentified modes: most of these are located in the region of pressure-dominated mixed modes; a few unidentified modes may also be ℓ = 3 modes. All components of the rotational multiplets intersect at 112 μHz; the m = ± 1 components intersect at 91 μHz. The oscillation spectrum is plotted in gray top to bottom in the background of the figure to link the stretched periods and the mixed-mode frequency.