Mylar "paper" tape, or use some other plastic that's known to have serious archival qualities.
Bulky, but if stable (enough) in the presence of water it'll survive various failure modes that would kill acid free paper. Of course you could etch Mylar or some other stable plastic to gain greater data densities like with the suggestions for paper. Just pick a plastic we know is seriously stable from actual experience, like we know with acid-free paper.
We also have such experience with emulsion based storage methods (microfilm, fiche, etc.), but those are rather delicate for my taste.
Mylar "paper" tape, or use some other plastic that's known to have serious archival qualities.
Bulky, but if stable (enough) in the presence of water it'll survive various failure modes that would kill acid free paper. Of course you could etch Mylar or some other stable plastic to gain greater data densities like with the suggestions for paper. Just pick a plastic we know is seriously stable from actual experience, like we know with acid-free paper.
We also have such experience with emulsion based storage methods (microfilm, fiche, etc.), but those are rather delicate for my taste.