Magic Photograph. Discontinued item from Tenyo. Delivered brand new and unopened. The photo should be completely black, but when you take a picture with a smartphone or other camera, the card appears. Of course, the audience can take pictures with their smartphone cameras, so it can be a memorable keepsake and a reminder of the magic (or, if it's a shop, a reason to think, "That was fun, I want to go again"). If the person shows it to friends, it can lead to things like, "This person is amazing!" or "I want to see it too," which can help with attracting customers and advertising. Without using any special electronic devices or gimmicks, you can achieve a tremendous effect with just this one gimmick photo. It doesn't take up much space, even if you keep it in your wallet, so it's a worthwhile item to have.