Yes, the Sony OA-D32 drives. Single-sided 600 RPM. One *could* argue,
that, given the data rate, it's already "high density" (of a sort). I
I would say it's normal double density (the spacing of the flux transitions
on the disk is the same as on a PC 720K disk) but a high data rate due
to the double spindle speed.
There's a double-head version too.
Not surprisingly I've worked on a lot of these drives, HP used them in many
of their HPIB disk units. There was a later half-height version (not a high density
drive, same format as the full height ones) which shares a lot of parts with the
Apple 800K drive.