Extension springs on steel
That matters because a door built in the early 1970s is almost always a single-layer steel sectional on extension springs mounted along the horizontal track, not the torsion bar over the header that became standard through the 80s and 90s. These are lighter doors, usually a single 9-by-7 opening or a 16-by-7 double, with stamped panels that dent rather than crack and hardware that was never galvanized to the spec used later.