This is a single die for forcing a specific number. It's been cleverly made to hide the secret well.
Imagine six envelopes, each numbered one through six. This die will force a certain number. Thus, the money would be placed in that "number envelope." A spectator can be made to win or lose depending on how it is presented. When a number is rolled, then that "number envelope" is destroyed. Through the process of elimination, the spectator will ultimately choose your desired number.
When ordering, note which number you'd like to force (1-6), so you receive the correct die.