Well, that's the residue of the last of my pin-feed continuous printer paper.
I bought a large box back in the early 1990s, I believe. And I finally used it up.
It has been a long time since I had a printer that required that paper. So I removed edges and and separated paper individually for a long time.
My old cat used to love these edges in a pile, leaping in like a kid with a pile of leaves.
Now I can use my new paper without guilt.
God, I'm old, aren't I?