[alnwlsn]

Related - this insane project to build the "most 3D printed" 3D printer [0]. The author has 3D printed mechanical components, motor windings, and a complicated electomechanical "motor controller".

The whole thing is intended to work from 3D printed punch cards.

I'm not sure how much of this project actually works, but it is interesting.

0 - https://clickprintchem.wordpress.com/2022/05/31/self-replica...

I'd probably also pick some kind of "punched" card; a print of some kind with holes in one place and not in another. The presence of a hole could be checked with a bed probe if everything was lined up correctly. I doubt the plastic would be intact for centuries like you want, but it would certainly outlast the printer you use to read it. A paper card would probably last longer though.

For high density, your best option is probably microfilm.

[anfractuosity]

Wow that printer is fascinating!

Good point re. film, related to that see - https://archiveprogram.github.com/arctic-vault/