Super Secret Encoder
/Behold, the super secret encoder. Each spy has their 3D printed encoder strip. Individually they are meaningless, but stack them together and the secret word is revealed. Other words can be entered if required.
You can create your own encoders using a little Python program that runs inside FreeCAD. The code is here: https://github.com/CrazyRobMiles/Python-in-FreeCAD
Might be fun for Christmas messages. It’s never too early to start.