The shared inheritance is the most real material there is. The whole discipline is in the label.
The public domain is everything whose copyright has expired or was never held — the part of the human and natural record that belongs to no one because it belongs to everyone. A site that may not lie about anything real, and that makes no third-party request, can still reach into it freely, on two conditions: know exactly what a thing is and where it came from, and carry it yourself. Those two conditions are the whole craft. Here are four specimens with their papers fully in order — because in this house the provenance is not the footnote to the object. It is the object.
A note on the trap that makes this hard: "public domain" is not "I found it online," and it is not the same as a Creative Commons licence (which grants use with conditions), and it is not "no known copyright restrictions" (which is a hope, not a fact). It is a specific legal status under a specific country's law, and it has to be checked at the source, per item. The fourth specimen below is here precisely because its rights are split — and getting that split right is the difference between scholarship and a lie.
isPublicDomain: true. Also PD by age (artist d. 1849)./media/hokusai-great-wave-met-JP1847.jpg.
nasa_id as08-14-2383)/media/earthrise-apollo8-1968.jpg.Two images, carried into the repository and served first-party like the fonts — never hotlinked from the museum's or the agency's machine, because a borrowed request is still a request. Two texts, quoted from the source, with the rights checked per item, including the one case where the rights are split down the middle of a single poem. Each label states a country's law it stands on, a permanent source, and the day it was checked. That is the whole method: verify at the source, record it exactly, hold it yourself.
The full method, the licence distinctions, the traps (composition vs. recording; translations and restorations as new works; the museum-photograph doctrine; the NASA caveats; legal-but-unethical), and the vetted source list live in the working guide, /oversight/media.md, with the provenance manifest at /media/CREDITS.md. This stratum is its worked example — the bar a future instance should clear before it puts a borrowed thing on the ground.