Want to see a trick?
Now, I have no idea where the coins go. You'd have to ask Johnny Wong. But I can tell you how they got back into the wallet: they never left.
This is an idea I had when I was thinking about ways to use e-ink screens for magic. E-ink looks a lot like paper at a casual glance, and red/black/white is a commonly available color scheme, so I'm sure I'm not the first person to think about using them for magic tricks. Of course, you probably can't make a single e-ink playing card since it'd be too thick (and I don't think you could do the rounded corners). But I was trying to figure out some way to make a card box or a wallet or something that could apparently show part of a card that was actually a changeable display.
I haven't prototyped anything like that yet, but it got me thinking about how I'd allow the card to be taken out without revealing the gimmick. Could the container appear to be empty even though it wasn't?
When I was like 12, everyone thought 3D TV was the next big thing. Well, the TV companies did anyway, I'm not sure anyone else really cared. In any case, my family bought a new TV around that time, and it came with a pair of 3D glasses.
They look a lot like the ones you get at the movie theater, but they don't work the same way. Instead of the simple polarizers you'd find in "passive" glasses, consumer 3D TVs generally use active shutter lenses. They're essentially one-pixel LCD screens that change from transparent to black over and over for every frame of video (which is why the glasses need batteries, unlike at the theater). By showing alternate frames to each eye, stereoscopic separation can be created. A similar technology is also used in some welding helmets to protect the user's eyes from bright flashes. And as it turns out, these LCD shutters are pretty inexpensive and readily available.
So naturally I did what any magician would do when working with a new technology. Put it in a wallet!
The electronics hide in one of the back pockets, disguised as a credit card. An electrical engineer friend helped me design the PCB; it's powered by coin cells so the whole package is quite thin.
When you press the hidden button, the window goes dark instantly. Then after a few seconds it fades back to transparent. And since the objects inside are real (not just pictures on a screen or something) they can immediately be tipped out, even by a spectator.
John Park wrote a guide for Adafruit about how to build something similar in the form of a wooden "mystery box". Besides that though, I haven't seen much online about using LCD shutters for magic. Maybe someday I can get a wallet like this produced as a commercial product. If any magic publishers are interested, please do reach out.