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:
Gadget169: "I'll have a X please Natalie247."
Natalie247: "This is a puzzling one indeed: At S46 12.XXX E169 38.YYY,
where XXX = (247 x 2) - 13
and YYY = XXX +60 ?"
Gadget169: "So X marks the spot at....."
Natalie247: "Correct - you won't need to store that away for later to see where i go with it."