Labeling blank HP 41 overlays

[Dave Britten]

I got a couple of the original white overlays - both with and without the shifted functions pre-printed - and some of the sticker sheets for labeling them. I'm trying to figure out the best way to label these. A 0.5 mm mechanical pencil directly on the overlay gives fair results, and is easy to erase if I want to change the assignments, though the lead can be smeared away fairly easily. The sticker sheets are about 50% blanks, and I can write on the blank stickers with an ultra-fine Sharpie, but even that appears to be prone to wiping away. Not to mention the stickers have a tendency to curl up at the ends a bit after applying them (I'm experimenting with removing and applying the stickers using needle-point tweezers to minimize curling). I'm hesitant to write directly on the overlay with a Sharpie, since I may want to change the assignments later. What was the usual go-to choice for labeling these things back in the day?