Crooked Gamblers' Tricks, November 1933
As long as betting has existed, so has cheating at it. In this article Popular Science advised against meeting strangers in a dark hotel room at night. Why? Because if you gamble with the scoundrels they might cheat.
The story tells the tale of a sucker getting roped in to a situation where the strangers used technology to see his cards at all times. Some other highlights include using invisible ink to mark cards, then putting on a pair of glasses to see the difference. The cheats might also try using a machine to imperceptibly cut the corner of a card, then know it by feel. The highest tech conceit shown is probably a mechanical card disperser that delivers a new hand to the player.
The upshot of it all is: if you absolutely must meet people you've never met before alone in a shady area, it's best to just leave your wallet behind.
From the article "Strange Inventions Used By Crooked Gamblers."