Continuity mistake: In the final hand, the first time we see Clancy's hand, it is the 8-9-10-Q of Diamonds; when the Kid calls, the cards are (a) reversed in order - Q-10-9-8) and worse, (b) throughout the entire movie, they are playing with Hoyle playing cards - but the reversed hand as well as Clancy's JD are from a deck of Bicycle cards, made by the United States Playing Card Co. In a real game, Clancy's hand would be dead, as it contains cards from an entirely different deck.
The Cincinnati Kid (1965)
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Directed by: Norman Jewison
Starring: Steve McQueen, Ann-Margret, Karl Malden, Edward G. Robinson, Tuesday Weld
Genres: Drama
Deliberate mistake: When The Kid visits the farm, the red truck in the background is a Fleetside truck that is definitely not from the 1930s.
Cincinnati Kid: Listen, Christian, after the game, I'll be The Man. I'll be the best there is. People will sit down at the table with you, just so they can say they played with The Man. And that's what I'm gonna be, Christian.
Christian: I know.