D5 AA 96: the meaning of these three bytes

Wow, that's going back a bit. It's also reminiscent of the issues associated with the 'hardness' of the formatting pattern used on floppy disks around that time.

Now this is stretching my memory so I stand to be corrected if wrong, but recall an E7 pattern was the default used in floppy formatting (on the the TRS80 and such), and this pattern was deemed as 'normal' hardness. (I'm unsure what formatting pattern Apple used.)

Those who wanted to ensure their floppies would pass a more stringent test (i.e. force bad sectors even if they were only marginally poor) would use a different harder pattern which was 6D B6. (If I recall this pattern and another of slightly different hardness (which I've forgotten) was mentioned in the NEWDOS80 manual, NEWDOS80 being a third-party upmarket drop-in replacement for TRSDOS.

"I will soon start a series of posts about the Apple IIgs, the most successful of the series." This https://retrocomputing.stackexchange.com/a/498 claims the 2e outsold the 2gs by more than 4 to 1. The former was in the market for far longer, was cheaper, and thus was the mainstay purchase for many mid/late-1980s schools.