One of my first products to market, the "Berkeley
Microcomputer
FlipJig",
was a plexiglass "pocket" with holes, for marking diskettes for
punching
the extra holes.
The "deluxe" model had a stub spindle on the outside and a ring, for
putting on hub reinforcers.
I guess this is not the deluxe model?
https://www.computerhistory.it/images/stories/storia/supporti/8inch_puncher.
jpg