[PatrickHenry]

Why was "a top secret clearance was required for his work at that time" (1967)? Was it SOP?

Back then, and presumably now, every officer had a background check and a security clearance. It was either Secret, or Top Secret. I've forgotten. Very routine. Even I had such a clearance. (Never needed it.) But for any particular bit of info, you still had to have a need to know in order to see it.

[browardchad]

Back then, and presumably now, every officer had a background check and a security clearance. It was either Secret, or Top Secret. I've forgotten. Very routine. Even I had such a clearance. (Never needed it.) But for any particular bit of info, you still had to have a need to know in order to see it.

Thanks for the explanation.