But Disk Utility did see the 1.44MB disk appear.

The Mac didn't initially seem to have any luck with the 720K disk (I later discovered that particular disk was probably dead, since Windows couldn't read it either).

The Micro Center staff was accommodating to let me try it out and see if my 1.44MB and 720K disks worked on Mac and/or PC. The back of the drive identifies as a Model: FD-05PUB. Disk Utility identifies this as the Y-E DATA USB-FDU (USB floppy disk drive). This drive is similar to the package I picked up at Micro Center for around $15 USD (just without the IBM logo). One of the drives was in a nondescript, tan cardboard box that was easy to open up. I visited a Micro Center and they had two types of external USB floppy drives available. User comments were varied in how reliable these drives would be with the disks. Buying a drive off the internet and hoping that it would work with 720K disks was a bit of a gamble. I found a number of products like this which claimed to work with 1.44MB disks, but most products were not very clear if they did or did not work with the older 720K format. Since I haven't owned a computer with a floppy drive in it for many years, I went in search of an external floppy drive that would be able to read both 720K and 1.44MB disks. Most of my floppy disks were 720K or 1.44MB disks for the PC, with a handful of 800K Mac formatted disks. The last time I had done an archive was back in the late 90s, so it was a good idea to go through this process while there was still the necessary hardware available to back up these old relics of digital storage. Last year, I took on the arduous task of archiving around 200 old floppy disks. Archiving Mac Floppies 7th May 2018 | Tutorial

Format floppy disk for mac os 6