Your question made me want to research the topic myself, as I'd never read too deeply into the Soviet pension system. I cannot provide much more than this source from the SSA regarding a joint US/USSR study on each-others pensions systems conducted in late 1958. But it does go into some detail regarding the structure of various benefits, how they were calculated, and administered.

Of course, the USSR went through many periods/reforms so I cannot say how accurate this characterization is for any given period or its efficacy for any given time and place.