Here is an example of one of the more down-to-earth cold war spy movies, written in the 1960s based on the book by Len Deighton. Written as an anti-bond, Harry Palmer (who isn't named in the book but had to be for the movie for continuity purposes), is an ex-con who was "so crooked he had to be put into intelligence". Blackmailed by Colonel Ross, his boss in the service, he is assigned to a new section when a top scientist goes missing and his handler is found dead.
If you look at this through the lens of the 21st century, the story doesn't hold-up that well. My advice: don't do that. Try to see it as a slow-burn thriller with great acting and twists and turns that are quite surprising. The production-values are excellent and camera-work and soundtrack (by John Barry of Bond-fame) is top-notch.