Radio Moscow QSL was quite an easy catch because they were blaring socialist propaganda 24x7 on a million frequencies. Probably too many people for the FBI to monitor back then before computers.
Radio Bulgaria must have been passing spy information through their broadcasts or something.
Radio Havana Cuba was not very active in english back then. After Castro took over, it was beamed to the US in english for propaganda purposes. Never got a QSL from them. I went on to get my ham radio license in 1958 and remember talking to several cuban stations before Castro. I got QSLs from them. After Castro, things changed.
BTW, listening to the socialist crap (propaganda disguised as news) back then reminds me how socialist (MSM) we have become during my generation.
LOL, nowadays it’s hard to tell the difference between MSNBC and the old Radio Tirana.