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Most likey: https://en.wikipedia.org/wiki/Numbers_station https://en.wikipedia.org/wiki/Numbers_station Mid way through the opening paragraph mentions several
by mbell 13y ago
Most likey: https://en.wikipedia.org/wiki/Numbers_station https://en.wikipedia.org/wiki/Numbers_station
Mid way through the opening paragraph mentions several people charged with spying based on surveillance of short-wave number stations.