I think that's a 'hard disk'. The floopys were round but your point equally valid.
That's an 8-inch floppy. When I was a co-op engineer in college in the early 1980s, the place where I worked had lab computers that used them, but they were already obsolete. Held 384k IIRC. That's kilobytes, not megabytes!
Looks like a 3.5" floppy disk to me.

