I sometimes forget that not all people are Magic players… ^^'
Anyway, Magic is a trading card game, I believe it to be the oldest. In this game you play the role os a planeswalker(think of it as a wizard) who battle another planeswalker in a battlefield. Your 'magics' are your cards and your goal is to take all the life points of the opponent.
Each player starts with 20 life points. And as you might think, it's a bit of a problem to keep track of each person's life points; some use a piece of paper and keep notes on it, some use 20-sided dice(not very reliable, a little bump on the table might roll it over), and some have bought a pack of cards wich include a lifecounter, wich is just a plastic device for you to keep track of your life points.
And that's what I'm trying to make here; it has to be of a very specific size, be sturdy, and most of all be simple to build. The two smaller wheels and the bigger one are the counting device(the larger one will have numbers around it), and the 'card' is the support for it.
I hope I was made clear enough :3