Charlie Miller, Max Malini, Dai Vernon/"The Professor", Larry Jennings, Nate Leipzig and Jacob Daley are all famous sleight-of-hand magicians. In fact, nearly every major male character in the film is named for a sleight-of-hand magician.
The hands seen performing card tricks in the beginning of the film belong to writer/director Damian Nieman (who's hand wears a spade ring), R. Paul Wilson, Jason England, and Earl Nelson, all real life card mechanics. Nieman also taught (along with Earl Nelson and R. Paul Wilson) Sylvester Stallone and Stuart Townsend how to perform their card tricks for the film.
Bo Hopkins' character is named John Scarne. John Scarne was also a famous sleight of hand artist during the mid-20th Century. He was best known for exposing crooked gambling to the public. In L'Arnaque (1973) he doubles for Paul Newman's hands.
In the beginning of the movie, you see a lot of card cheating devices that have been used throughout the 19th and 20th centuries. Among them is the Kepplinger holdout device which was the most popular card cheating device used.
Hal Holbrook's character, the Professor, is based on the magician Dai Vernon. It is Vernon's portrait on the wall of the Magic Castle where the Professor is sitting.