So, there is this building near me, 51 stories, opened in 1965. Does anyone have any ideas on what fire alarm panel was originally installed in the building in 1965?
It possibly could have been some sort of relay based AC system.
Yeah: such systems were common then.
This question is too broad, if you can get down to something specific like a brand, that would help significantly.
The best way to know is to try to find pictures of the building while it was being built and/or shortly after. If the construction company that built the building is still around, they might have records of what the building systems, including the fire alarm systems, were at the time of building.