Code wheel
Copy protection made of cardboard: two rotating discs in the game box that you aligned to look up a code the game demanded.
By requiring something from the physical package, the code wheel sidestepped the core problem of the 1980s — the disk could be copied, but the contents of the box could not. The game asked for a combination, the player turned the concentric discs until two symbols met, and read the code off in a window.
The most famous is LucasArts' "Dial-A-Pirate" for The Secret of Monkey Island (1990), where a wrong code eventually got you hanged. The scheme died once cracking groups simply tabulated the entire wheel and shipped the table with the crack, and once the CD made manual checks pointless.