Just came across this interesting short documentary "The Ultimate Radio Mystery" on YouTube about the numbers stations, some of their history and documentation of stations that are currently operating. It also leads to a web site http://priyom.org/ which is very interesting and associated with tracking these numbers stations and their activities. This is old news to some of you, I know, but I found it interesting that many of these stations still exists and operate today. There is also some advancement in decoding these encrypted transmissions from various countries as documented in the Priyom.org web site (eg. North Korea). I remember as a kid tuning around on the shortwave receiver hearing many of these monotonous numbers stations rattling off groups of numbers for hours at a time. I never could figure out what the point was.