You can write your name, most used password (what can go wrong), phone number, favorite joke… on this 16 bytes keyring punch card. If you print many, and thread them, you can even carry an entire book of information.

Poke through and the holes will open easily. 

Use the ASCII table to code and decode messages, it even contains the binary code for each character. (In the accompanying table the first 128 characters are standard ASCII, the next 128, typically called extended, were chosen by me).

Ideal for teaching how the binary system, bits, bytes, and computation in general works.