  The explosive origin of the young supernova remnant (SNR) 3C 397 (G41.1-0.3)
is debated. Its elongated morphology and proximity to a molecular cloud are
suggestive of a core-collapse (CC) SN origin, yet recent X-ray studies of heavy
metals show chemical yields and line centroid energies consistent with a Type
Ia SN. In this paper, we analyze the full X-ray spectrum from 0.7-10 keV of 3C
397 observed with Suzaku and compare the line centroid energies, fluxes, and
elemental abundances of intermediate-mass and heavy metals (Mg to Ni) to Type
Ia and CC hydrodynamical model predictions. Based on the results, we conclude
that 3C 397 likely arises from an energetic Type Ia explosion in a high-density
ambient medium, and we show that the progenitor was a near Chandrasekhar mass
white dwarf.
