Here we have two diagrams of the Nagasaki atomic bomb (Fat Man) based on information passed on to the Soviets from Klaus Fuchs and other spies. These aren’t particularly sensitive today, but would have been Top Secret–Restricted Data when they were acquired. On the right is the basic dimensions of the body of the bomb, and on the left is a more detailed arrangement showing the electrical systems inside the bomb. As anyone reading this blog no doubt knows, the Soviet Union had a number of spies in high places in both the US and UK sides of the Manhattan Project, which they dubbed “ENORMOZ” in their code language.

http://blog.nuclearsecrecy.com/2012/07/27/rare-photos-of-the-soviet-bomb-project/