Isobel (preliminary ESI): z=0.511 (galaxy OII, Hb, OIII) Ia features good when galaxy template subtracted. Weak SiII though.
Andy (preliminary ESI): I agree that this looks like a Ia at z=0.511. See my 50 pixel median-smoothed, galaxy subtracted spectrum: Vivaldi.90n.m7.ps. Note that since this is median-smoothed that peaks/valleys may not be as high/low as they should be. It is somewhat alarming that there is hardly any evidence for Si. This is probably why 90N is a good match, though Vivaldi is probably closer to maximum light.