Projected model spectra for the SN-in-the-WBB scenario near the limb (red) and toward the inner parts of the nebula (blue). The gas near the limb has a larger ionization parameter than the bulk of the volume and accordingly lacks oxygen lines, but features the lines of Ne, Fe, and Si. In reality, S147 is far from spherical symmetry and a mixture of components with a range of ionization parameters should be observed.