At the beginning of the 80s, I worked for a while in the Engineering Dept. of a large defense plant, owned by an even larger corporation that was a household name back then. They had a practice of regularly recruiting new and recent graduates and every summer there'd be "new blood". It was generally understood that the newer employees would fraternize. It was their first experience not only living on their own but having a real income. Even back then I had heard it said you shouldn't date co-workers, but at that place nobody seemed to object. I know of one young woman who married her boss who was substantially older (at least 15 years I'd say) and to my knowledge the marriage lasted although I wouldn't know if it lasted forever. Another thing to consider is that back then the security requirements to work there were much less stringent than nowadays. Very few positions required a Top Secret clearance, and typically you began the background investigation process (usually for a Secret clearance) after you started work. That is not the usual situation at such places nowadays.
When I started I had prior experience and was hired directly as opposed to being brought in via the "new grad" program but was told later I might have still technically qualified for that.
Anyway, like I said it wasn't frowned upon to hit on co-workers. I suppose an exception would be made if you continued to make unwanted advances but office romances were common. I once asked out a co-worker I found attractive, who was actually a couple years older than me, out. It turns out she wasn't interested but a "new grad" who was temporarily living in her basement wanted a date with me and wasn't the least bit shy about it. I went out with her off and on although things didn't get really serious with her until after I was no longer employed there. Before that happened, she was in a relationship with another co-worker but unexpectedly called me after they broke up. She was more than 6 years younger than I and eventually admitted her interest in me was primarily physical. I hadn't been much attracted to her at first, but her unselfconscious displays of physical affection led me to develop the "hots" for her very quickly. This is why I've tried to tell other young women that straightforward expression of physical desire for a guy who seems hesitant will probably bring him around, despite concerns that it will scare him away.
There was another young woman there in whom I was interested, but never developed more than a platonic relationship. It turns out she was romantically interested in me but never gave me any recognizable sign. I found out because after my engagement had been announced in the local Jewish newspaper, I happened to run into her in a store and she told me at that time she had always hoped we'd become a couple. I still don't know what to think about that. I don't think she'd have been the right person for me to marry but I'll never know. BTW even telling me that, she wasn't at all emotional about it. I also happen to think she was likely on the spectrum.
Much of what I've said is directly relevant to this thread but it's what comes to my mind whenever the topic of workplace romance arises. I will say though, that this is an area in which today's morality seems to have become much less permissive than when I was dating age. The number of sorts of situations in which it is deemed improper for two people to become romantically involved seems to have grown, at least for heterosexuals, reducing opportunities for everyone.