Re: as I recollect
Blank 5.25" had a cut out ready in hem (regardless of the 'size') and a pack of little silver tabs to cover he whole when you wanted to write protect it.
"Disk notcher"s were a device you used on the 51/4 to cut a hole in the side of the smaller value disks so they'd act as a larger one. The original single-sided disks had this hole so they'd not work in the drive upside-down but it was believed the 'platter' had the same surface on both sides, so 'notching' it and turning it upside down meant both sides could be used.
https://www.worthpoint.com/worthopedia/1-25-floppy-disk-notcher-best-ebay-142512389
https://en.wikipedia.org/wiki/Floppy_disk#8-inch_and_%E2%80%8B5_1%E2%81%844-inch_disks - note the text "Punch devices were sold to convert read-only disks to writable ones and enable writing on the unused side of single sided disks"
And a spewboob vid I haven't watched :
Biting the hand that feeds IT
