Mid-to-late 1960s drums
That narrower build window matters because it means a lot of doors here still run on the extension-spring cable drums that were standard hardware in the mid-to-late 1960s, not the earlier torsion conversions you find on the oldest streets closer to the city center. When a cable on one of these goes, it's usually a snap at the bottom bracket where the cable clamps to the door, or fraying where it winds around the drum.
