Chris (preliminary): Most likely a type Ia at z~0.5
Isobel (preliminary): IMH: Very strong OII at z=0.510. Early SNIa features match well. See Massenet_snz.ps
Chris (final): SN Ia z=0.511 OII
Andy (final): Certainly a Ia due to the 6000 A (observed) Si feature. The best match is to 94d at +2 days for z=0.49. This is 0.02 off of the OII feature observed by Isobel and Chris, and it isn't because of the redshift of the template -- 94d was at z=0.0015. Possibly it is due to unusual velocities. See S01-035.94d.p02.ps, where the data have been S-G smoothed. Note that 94D was a normal SN Ia, but it was very blue (Patat et al. 1996, MNRAS, 278, 111). Even though, SN 1994D was similar to SN 1992A, SN 1992A is not a great fit because the "emission" feature at 6800 A observed is lower in Massenet than in 92A.
This Ca feature is somewhat similar to the depth and width of the feature in SN 1981b, but if you match up these features using 81b as a template, then none of the other features match. The Ca II absorption at ~5500 A observed, 3700 A rest, seems to be deeper, broader, and more blueshifted than in 94d. (Note that this absorption is not due to TiII as in SN 1991bg and SN 86G.) This indicates that Massenet may have had unusually high velocity Ca, perhaps like 84A (though I don't have the 84A spectra).
Another reasonable match is SN 1990n at -7 days, though again if you match up Ca, then the other lines are off. Note that strong, high velocity Ca is a signature of certain types of SNe Ia, like 84A, but it can also be a sign that this spectrum was taken at an early epoch. See, e.g. Hatano et al. 2000, ApJ, 543, L49