Superfit comparisons of PTF10iam with the Type II SN 1999em (from Hamuy et al. 2001; top) and the Type Ia SN 1999ac (from Garavini et al. 2005; bottom) with best-fit extinction and host-contamination corrections applied. The fit to SN 1999em matches most of the spectral features, except for the absorption feature near 6200 Å. The SN Ia fit is able to match this feature as Si II, as well as other features in the spectrum, with the major difference being that PTF10iam has additional broad hydrogen emission lines (insets show the difference between the superfit host and extinction-corrected spectral fluxes of PTF10iam and SN 1999ac around the denoted hydrogen lines; zero flux is marked by the horizontal dotted line; the narrow features are from the not-fully-subtracted host of PTF10iam).