...OPERATION GHOST STORIES...
...CHECKERBOARD CODE...
...A treasure trove of images, videos, and documents from the FBI Vault...
This information provides case studies and names of those who, over the years have been involved with foreign intelligence agencies notably the Soviets.
The header image is one of two from the files, a neat example of clandestine communication techniques. Here's the second image:
And as promised here are the 3 links that give access to the Vault and its fascinating collection of real-world espionage artifacts:
I am certain that you will find the contents of the FBI Vault very useful especially if you are interested in the history of Soviet Espionage techniques. The real world of their work is far removed from the stories you may find at the movies and on Netflix etc.
At this time our intelligence services, whilst having some information available, tend to keep things under wraps for a lot longer.