40-track, single-sided, 256 bytes-per-sector
35*256*16 = 143360

We should have mostly 16 track ones. The 13 sector ones come
from the old Apple ][s in the old Lyceum server room.

links
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https://en.wikipedia.org/wiki/List_of_floppy_disk_formats
http://cowlark.com/fluxengine/doc/disk-apple2.html