Mid-90s torsion hardware
By the mid-90s, extension spring setups were giving way to torsion springs mounted on a single center shaft, and tracks were rolled galvanized steel bent to a radius that assumed a specific roller size. That's the detail that matters for an off-track call: the track wasn't built to flex, and thirty years of thermal cycling in a cold-winter climate leaves the mounting brackets a little looser than they were the day they went up.