That might be it, as the mentioned commie blocks I lived in are all in Poland. I don't know if the dials were there during communism as well, but I remember no

That might be it, as the mentioned commie blocks I lived in are all in Poland. I don't know if the dials were there during communism as well, but I remember noticing that the radiator in my school did not have one (save for a hex key valve) and thinking it was unusual, so they were already common in the mid 90s.