The original “clamshell” iMac shipped with a set of Stickers for programmable function keys in various icon designs. These stickers were designed to be used above the top row of F (function) keys across the top of the iBook.
Many of the iBook F-keys were pre-assigned:
F1 and F2—brightness (down and up)
F3 and F4—volume (down and up)
F5—num lock (number lock to allow use of a built-in number keypad)
However, the F7–F13 keys were unassigned. Using the Keyboard System Preferences, users could easily assign functions to these keys. The set of stickers were included to allow users to mark the functions with a custom sticker to help them remember the key’s function.
Although these stickers shipped with all original iBook “clamshell” laptops (blueberry, tangerine, graphite, indigo, and key lime), I have found no Apple documentation that explains their use. I have two versions of the stickers, a blue-gray set from the original iBook release, and a light gray version from the later iBook models.