On my fully manual '50s Leica M3 rangefinder camera, the ISO film speed indicator dial on the back only goes up to 200 - the fastest speed available at the time. With film speeds going up to ISO 3200 now the dial is basically useless so I don't bother with it, but then I have to remember what film I loaded last time I used the camera - which might be weeks ago. So, was it Delta 3200? Was it T-Max 100? Or maybe Neopan 400? Oops.
After screwing this up a few times too many, I modified gcardinal's hotshoe covers by adding ISO speed numbers to the top. Load your camera, swap out the cover for the right ISO, and never forget what film is loaded again!
The hotshoe covers should be fairly universal, so you don't have to own a Leica to use them. Give it a try. This set contains speeds 100, 125, 160, 200, 320, 400, 800, 1600 and 3200.
The text is raised and easy to color with a few swipes of permanent marker. Tip: if you print 2 sets, one in white and one in a color, you can even remember if you have B&W or color film loaded.
Printed with the default recommended settings of Cura for my machine.