Two (of the many) mind-blowing discoveries of the 80's:

1. there was a disk notcher (the Nibbler?) that would DOUBLE the capacity of a 5 1/4 floppy!

2. you could just use a regular paper hole punch and a few select clips to do the same thing!

All my C64 floppies had faint parallel pencil lines across the top to line up the slots and what looked like mouse-nawed holes on one side.