Looks like near-IR of some sort but media calls everything x-ray since it's what people know. X-Rays would go through cards anyway. But you'd get nice pictures of peoples hands though, and cataracts after a night of play.

edit: now I think of it: if the cloth is thin enough you don't even need near-IR. Old fashioned IR camera's (those without any fancy filter) from the '00 showed though some relatively thin opaque synthetic material with a tiny IR source so ...

The table didn’t actually use X-rays. They’re using X-ray to mean it could be seen through with special cameras, perhaps IR sensitive.

I don't think it's literally "X-Rays". A couple years ago I saw an infrared transparent table being demonstrated as a product prototype by a distributor of magic props at a conference for professional magicians. I played with it a while because I thought it was quite remarkable and had never seen anything like it. The top surface was a half-inch thick hard black plastic which appeared completely opaque. It was perfectly convincing as it even had faux wood grain texturing on the surface. It looked for all the world like a table you'd see at IKEA or Target. I put my phone's flashlight on full brightness under it pointing up and couldn't see any light coming through, even shading the spot with my hand.

The table had a bunch of IR emitters pointed up built into the supports holding the table surface but they were at least two feet away and well-obscured into the table leg design by more normal-seeming smooth plastic I associate with being IR-transparent. Of course, if you suspect the use of IR, it's quite easy to detect with your camera phone. There was a camera hidden into the middle of the table supports looking up which transmitted the image wirelessly to a monitor nearby. My own face-down playing cards were visible on the camera plain as day, so it doesn't require special cards.

Interestingly, the magic distributor showing it wasn't giving out any info on who made it, what it cost or when it might be available. They just said they were "showing it to gauge interest" and might carry it at some point in the future. They're a large, long-time, reputable distributor of other people's products so I don't think they were involved in creating it. It hasn't made an appearance at subsequent conventions, so they must have decided it wouldn't be popular with magicians - which makes perfect sense. It would have been expensive and pretty technically involved for a limited-use magic prop. Good magicians have a many easier and cheaper ways to learn the identity of hidden cards :-). But the fact such a thick, textured, optically opaque surface could be IR transparent was pretty nifty.

As a former magician I was surprised to read the gang was using 'reader' cards (backs marked with ink visible to special glasses). No one uses those anymore as there are so many better ways to do the same thing. Seems like this gang was just into various tech toys and kind of lazy. In reality, once you control the environment, cards and have confederates in the game - cheating to win is trivial without any tech if you know what you're doing.

Next podcast sponsor fad: lead-lined underwear. PbUndies

Nothing like a night of high profile illegal poker while getting blasted with radiation. /s

i wonder if we're not conflating xray with terahertz radiation perhaps? the former being used by a company called corrections one that produces a horrifying whole-body X-Ray of a prisoner to detect contraband (certainly not healthy.)

Terahertz radiation is used in airports with (arguable) safety and efficacy. the resolution is sufficient to read protest statements written under a passengers shirt in metallic ink. I wonder if it could read cards should they be specially crafted similarly.