Inside the agency's headquarters is a museum filled with relics from half a century of cloak-and-dagger exploits.
David Wise in Smithsonian Magazine:
A chill wind whipped off the Warnow as a retired railroad worker shuffled through the streets of the port city of Rostock one winter night in 1956. He wore the drab clothes typical of East German residents. But when a second man appeared from the shadows, the elderly German revealed that he was wearing a pair of distinctive gold cuff links embossed with the helmet of the Greek goddess Athena and a small sword.
The second man wore an identical pair. Wordlessly, he handed the German a package of documents and retreated back into the shadows. The German caught a train for East Berlin, where he handed the package and the cuff links to a CIA courier. The courier smuggled them to the agency’s base in West Berlin—to George Kisevalter, who was on his way to becoming a legendary CIA case officer.
The man who retreated back into the shadows was Lt. Col. Pyotr Semyonovich Popov, an officer of the GRU, the Soviet military intelligence agency. Three years earlier, Popov had dropped a note into an American diplomat’s car in Vienna saying, “I am a Soviet officer. I wish to meet with an American officer with the object of offering certain services.” He was the CIA’s first Soviet mole, and Kisevalter was his handler. Popov became one of the CIA’s most important sources through the 1950s, turning over a trove of Soviet military secrets that included biographical details on 258 of his fellow GRU officers.
It was Kisevalter who had decided on the cuff links as a recognition signal. He gave them to Popov before Moscow recalled the GRU officer in 1955, along with instructions: If Popov ever made it out of the USSR again and renewed contact with the CIA, whoever the agency sent to meet him would wear a matching set to establish his bona fides.