1960s-70s lighter door hardware
That transition matters because it decided what kind of spring hardware got installed. A lot of these houses still run torsion springs sized for a lighter, thinner-gauge door than what's often hanging on the track now after a replacement job somewhere down the line. When the spring finally lets go, it usually announces itself the same way: the door slams down the last foot instead of settling, or it won't budge past waist height when the opener tries to lift it.
