Gambler's Dilemma is a classic Chazpro product from nearly 30 years ago. We've made a limited number of this golden oldie.
Offer a short demonstration on a new card marking system for near-sighted people. Demonstrate with six cards, clearly showing their faces. The backs are clearly shown to have large numbers drawn on each, representing their faces. The only problem with this system is the "6". When it is turned upside-down, it looks like a nine, which, if you are a magician, will automatically change the face. Show the marked "9" has changed to a nine on the face. Show the remaining cards front and back, there are only five! Replace the nine, turning it around so it is a "6" again. At the finish you shows the fronts and backs of the cards again, the nine is gone!
The instructions offer different handlings, from easy to moderate. There are also suggestions for extending the routine.