[OSM-talk] Licence of Soviet military topographic maps

[Liz]

On Thu, 1 Jul 2010, Apollinaris Schoell wrote:
> just checked one of these maps. and interestingly it contains data which is
> most likely copied from official maps which are not in PD. So it is nearly
> impossible that these maps are PD. the russian copyright holder may have
> bought the source data but very unlikely they have a license for
> distribution and release to PD.

Now I show my ignorance, but I am assuming that the last major name changes 
for cities and streets in Russia was post-Stalin, with a few changed after the 
breakup of the USSR.
Am I correct?
and now ... what years would be the markers for these events?
Because some of post-Stalinist changes would now be expired from copyright?