A small 50ml pill container.
This cache is part of the Blockbuster A to Z series.
An old 80's gameshow in which contestants had to pick letters and answer questions relating to that letter to get across the board and win.
If we were doing a modern day geocache version of this I would imagine it would go:
sirbennis: "I'll have a C please Natalie247."
Natalie247: "Which C has been designed to help orient new players to the ethos of the geocaching community and to guide experienced players in questionable situations, so that everyone can enjoy geocaching?"
sirbennis: "It's C....."
Natalie247: "Correct - you might want to store that away for later to see where i go with it."