I find seven IS-7 paper "projects" from Ob.254 to Ob.260 in 1945, about twenty Test tank (guns and engines configuration) of the last one from 1946-48, but no production model.
I will double check...
Well then your knowlege and sources is a lot better than mine then, i only knew of the model 1946 and 1948 for the is-7 (and i double checked, model 1946 was just a wooden mockup), so you are mostly likely correct here.