There are two alternatives, a high-mass 25-40 solar masses star or smaller star with mass of 8-10 solar masses. As there is no evidence that neutron star was formed during the collapse of the star, it is likely that star was in upper spectrum of the mass.
Observations of the light curve from SN 1997D showed no evidence of other energy sources in the expanding supernova envelope therefore it is unlikely that a Neutron star was created, all the evidence leads to the creation of the stellar mass black hole of approximately 3 solar masses.
From twilight to highlight: the physics of supernovae : proceedings of the ... By Wolfgang Hillebrandt, Bruno Leibundgut
The fading of supernova 1997D Benetti, S., Turatto, M., Balberg, S., Zampieri, L., Shapiro, S. L., Cappellaro