A quick search on Google for “panel game” and “con” tells me about a lot of science-fiction conventions… and nothing that I can see about the confidence game.
I find a lot of references to “panel game” in British TV sites – it seems to refer to game shows. One example from the BBC:
All over the Shop
Comedy panel game in which Paul Ross invites two teams of celebrities to test their shopping skills, such as identifying slogans, spotting fakes and rooting out rip-offs. With Vicki Michelle, Bob Downe, Maria McErlane and Simon Gregson
I can see it now. It’s the 1840’s, and Alec Hoag is standing on the stage, illuminated by a candle-lit spotlight. He stands in front of an oversized Wheel of Fortune, while backstage French Jack awaits the signal.
“So, Roy,” Alec says with his eyes gleaming, and twiddling his thin mustache. “You’ve won two hours with the prostitutes. Are you staying put with your winnings, or are you willing to bet it all on… an hour with the lovely Melinda?”
The spotlight shifts upward to outline a lady dressed in feathers, and not much else. A multicolored cape of feathers covers her back, and sweeps down to form a tail, while her long legs and arms are free. Her white skin glistens with moisture. She smiles down at Roy.
“Oh, yeah, yeah, yeah… I’ll try for Melinda…” Roy drools.
Alec gives the wheel a mighty spin, and nods back to Jack. Jack pulls a wire, and a weight on the back of the wheel falls. The wheel slows down, and stops at ‘Lose all’.
“Oh! So sorry. You’ve lost your hundred dollars. Better luck next time…”