This is a pre-owned effect that is in good working order and comes with its original instructions.
Effect: The spectator is given a number of double sided and different colored chips and is asked to stack them so that the same colors are facing each other, (example, red on red and green on green, etc.) and when they are all stacked they are asked to cover them with two blank cover chips.
The magician will always be able to correctly tell what colors are at each end of the stack! The possible outcomes are many and the spectator is not forced into how they start to assemble the stack of chips. It’s a truly a free choice.
The trick can be performed over and over again and each time a different color will be at each end of the stack!
This actually becomes more perplexing if it is repeated a few times!