Foolscap and onionskin
Just re-reading Wizard of London, and a phrase jumped out: she put the "foolscap into the drawer." I thought, taken out of context, how many people know that foolscap is a type of paper? (Used for handwriting, it is about 8x13 or 8 1/2x17, depending on your source of definition.) I haven't gone on a search to buy it, but I suspect it would take a specialty store and probably special ordering to obtain.
Some years back, I wanted some onionskin paper. I could find it only on-line, yet it used to be so common that the local drugstore carried boxes of it. Apparently onionskin went the way of carbon paper, into limbo along with the manual typewriters.
We can find fancy papers in all sorts of designs and colors and finishes and weights... around here, sold by the sheet or the 5-sheet packet, in craft stores. But onionskin doesn't rate their notice.
There isn't much that I miss about the "old days", but the lack of onionskin paper seems to have left a hole in my world.