1.3GB removable disk.

Fujitsu Limited introduced the 1.3GB 3.5 inch magneto-optical (MO) disk in 1998.
A laser heated the disk surface such that a magnetic head could magnetise a bit of the surface.
When the surface cooled the magnetisation was fixed. The disk could be formated in a variety of ways.

This is a front view, written on the label is "Backup 25/12/00", someone is busy on Xmas day.
The disk did not require a special device driver, it behaved like a normal hard disk

A rear view of the disk with a WRITE ENABLE/WRITE PROTECT switch at the bottom right.

The spring loaded protective cover slid to one side when the disk was loaded in the drive
to expose both the disk surface and the central hub

There is an interesting pattern on the disk.
The disk was slow to write because it took three passes:
the first pass to erase the previous data,
the second to write the new data,
and a third to read back and check what was written.

Once written it was no slouch, data transfer was 3.5-5.9MB/sec at 3214rpm.
As FUJITSU said "The MO disk media can be rewritten more than 10 million times and
stored for very long periods of time. The media offers superior resistance to physical damage,
contamination and outside sources of magnetism, providing a high degree of reliability."

So it was good media for some applications such as the long term storage of records, legal/medical etc.