Throughout the Cold War these number stations could be heard on short-wave radio frequencies. Although there continues to be many theories including conspiracy theories no one knows where these stations are or what the numbers mean.
What Happened to the Numbers Stations? – Spying by Numbers?
Alan Malcher 
As information on number stations is generally classified, very few government organizations have released information about them. Those that have include the Czech Office for Foreign Relations and Information (https://tinyurl.com/yyzxrmr9), the Polish Institute of National Remembrance (http://numbersoddities.nl/N&O-200.pdf), the Swedish Security Service (https://tinyurl.com/y256ks83), and the National Archives of Latvia. Additionally, number stations have been involved in the publicly prosecuted espionage cases of Kim Hyon-hui (1987), Václav Jelínek (1988), the Cuban Five (1998), Ana Montes (2001), the Illegals Program (2010), and Andreas and Heidrun Anschlag (2011).
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Giles, always great to read your valuable input. Many thanks
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