An aperture card! Used as a very early image tagging/sorting system, you'd have microfilm mounted in a punch card, so you could have a regular punch card organizer/sorter find your images. The DoD loved them because they could store tons and tons of engineering blueprints in an organized, computer-sortable and -searchable way.

Image source

foone on Twitter

“Because I took some pictures for a reply to a locked account, some obligatory beauty shots of an aperture card, which are a fun combination of microfilm and punch cards.”

Twitter
@nytpu ooh it’s like holding a file
@nytpu as a data storage enthusiast, I agree with them, this is cool af and I would definitely love to have a computer sorting system for that in my basement