This is a version of the old ‘pea house’ trick. The close-up magician shows a small metal bottle and a ball bearing. The ball bearing is dropped in a hole in the bottle. When the magician turns the bottle over, the ball bearing doesn’t drop out. However, whenever a spectator tries this, the ball bearing falls out. Complete with instructions.
The poster advertises a comedy magic show in Vienna in 1976. Wittus is Wittus Witt.