On Sun, 8 Mar 2020, Warner Losh wrote:

> That's why I got a kyroflux...  too hard to find an old enough pc that 
> the floppy controller supports the full range of crazy that once roamed 
> the earth...

There were also many devious copy protection schemes used for games etc. 
One common one was to punch a hole in a known sector (!) and if you didn't 
get a read error when accessing it then it was an illegal copy; another 
was to store data in an otherwise unreachable sector e.g. track 41 on a 40 
track disk...

In short, good luck :-)

Hmmm...  I just looked up the KryoFlux, and it's a fascinating device; it 
actually gets right down to the flux level!  I've never seen a 3" disk 
before though.

-- Dave