used to repair the drive controllers for them and recalibrate the belts. They had a big, huge stepper motor inside that was driven by a little rubber belt. Eventually the belt would stretch and the drive would go out of calibration. We had a special program that sent signals to the controller that could be monitored on an oscilloscope. The 4-dots had to line up in a certain pattern to ensure the drive was in calibration. Now for the disks that were written while the drive was out.. Oh well that was up to the customer to figure out.

What was funny is my old Varityper Epics 20/20 typesetter came with one of those drives in it. Our whole type library loaded from a dozen of these disks on to a 20MB Winchester Drive. The program and proprietary OS loaded from another 30 disks. The hard drive was Miniscribe but the company referred to the drive as a Winchester Disk.