FWIW, Back in the late 70's I had relatives working in the Pentagon, specfically weapons development. I won't say which branch.
I came to visit when I was 17 and they took me to work with them everyday for a week. A simple, "he's with me" got me through checkpoints and security and I'd send a couple of hours hanging around the offices then I'd head into DC for the day.
I remember there were counless open file drawers with combo locks and files marked "TOP SECRET", many of them were left open with files hanging out like it was an accountants office on April 14th. I know times have changed but I got a big laugh out of seeing all the TOP SECRET files labeled "Project XYZ" and such just laying around the office.
Your name's not Ellsberg is it? (grin).
I used to visit my husband when he was standing duty; for awhile aboard a sub, then in offices. He'd never tell me anything! If he had to go to the bathroom someone would babysit me, or if no one were around I had to accompany him inside the bathroom.
There was one room in the building with a black door, peephole, and surveillance cameras outside. I was DYING to know what they did in there! LOL!
Yeh, and all those documents had cover sheets, indicating the level of classification. I'll wager that you only saw unclassified titles and did not see the actual classified material.
About that same time I was working on a "Black" project (it later went "checkerboard", and was the Navy A-12 development program). We didn't let "uncleared" into the area without a minder. When they were there we had rotating strobes on the ceiling that would be turned on. When they came in, their keeper would yell "UNCLEARED" and the person had to carry around a "beeper" which also had it's own flashing light. Earlier and at another facility the keeper had a bell that had to be rung every minute or so. We did not let any relatives or others with no need to be there into the area. The uncleared were mostly people come to service the computers, the wiring or the HVAC. Even the cleaning lady had a clearance in the first case. In the second case, which allowed open storage of documents, since it was inside a "vault", we had heavy black plastic sheeting which we threw over everything the night the cleaning crew was to be in. They still had minders of course.
From what I've read the stuff the Bergerler compromised was "Code Word" material, which is more heavily protected than general Secret or Top Secret material.