My mom did translations on an IBM display writer that used 8” floppies. They were the floppier big brothers to the 5.25 “floppies” of the Apple/commodore and early pcs. Those 3.25 had a much stiffer shell. You are right that the disks inside were the same material.

Over $7500 in last century dollars for a device with 160kb. I believe it auto saved though.

https://en.m.wikipedia.org/wiki/IBM_Displaywriter_System