In the room where live coverage of game one was being announced, after all the men leave, the announcer states the final score, calling Cincinnati's team the Red Legs. They weren't called the Red Legs until 1944.
Just before the first game in Cincinnati, Buck Weaver and Kid Gleason are talking at home plate in the empty ballpark. Buck swings a Louisville Slugger with a "Powerized" label on it. Louisville Sluggers got that label in 1931.
In Charles Comiskey's office, after word of the scandal is out, Comiskey's lawyer bounces an autographed Rawlings baseball. During the Black Sox scandal, A.L. Reach was Major League Baseball's official ball.
Early in the film, a close-up shows Eddie Cicotte's right hand as he prepares to throw his famous "shine ball." A "Rawlings" logo is clearly visible. In 1919, Major League Baseball exclusively used Spalding baseballs. They switched to Rawlings balls in 1977.
Dickie Kerr tells Kid Gleason that he remembers the first ball game he ever went to, where Gleason pitched a no-hitter to beat Cy Young 1-0. Kerr was born in July 1893. Gleason became a full-time infielder in 1895. He pitched for St. Louis, Kerr's home town, in 1892, 1893, and 1894. Kerr could have attended a game where Gleason pitched, but he probably wouldn't remember it. Plus, Kid Gleason never threw a no-hitter.
In the film, Fred McMullin's role in the scandal is completely incorrect. McMullin overheard Chick and Swede's conversation in the locker room, not the bathroom, in August 1919. While McMullin was a friend of Swede's, he was only included out of fear he'd tell Gleason about the fix. McMullin earned his $5,000 by grounding out in game 2 with catcher Ray Schalk in scoring position. McMullin told Swede and Chick that he was going to tell the mafia that Swede and Chick were having second thoughts about throwing the series. From then on, McMullian served as an unofficial liaison for the mafia. The players were forced to throw several key games during the 1920 season out of fear of being exposed.
During the trial, Buck Weaver exclaims he batted .327 in the World Series. He actually batted .324. Weaver's lifetime World Series batting average was .327, but he batted .324 in the 1919 World Series.
An overhead shot of the field before the conversation between Weaver and Gleason, on the day before the World Series opens, shows the obvious remains of the lining for a football field. At the time, Cincinnati had no football team that would have played at Crosley field.
In game 7 of the World Series, the scoreboard in the background says that the Cincinnati Reds scored their only run in the bottom of the sixth inning. They actually scored that run in the bottom of the fifth inning.
During the first World Series game, the scoreboard in the bottom of the 4th inning says Reds 1, White Sox 0. The score should have been tied 1-1.The Reds scored one run in the bottom of the 1st inning, and the White Sox scored one run in the top of the 2nd inning.
In the movie, Hughie Fullerton and Ring Lardner work together and separately during the games (while they are reporting) to mark down any fishy plays or players. In real life, Christy Mathewson worked with Hughie Fullerton.
When the players meet their lawyers for the first time, the head counsel introduced his co-counsels by comparing them to famous ballplayers (i.e.: "The Ty Cobb of lawyers"). One player asks, "Who is the Babe Ruth?", and the head counsel replies "I am." In the time line of the film, between the 1919 and 1920 seasons, Babe Ruth would've just completed his final season with the Boston Red Sox. It was his first season playing more than 100 games, and he might not have been as famous as he became later. However, the players were indicted after the 1920 season. In 1920, Babe Ruth became the first player to hit 50 home runs in a season. He also set a hitting percentage record that stood for more than 80 years.
Cincinnati is the first team shown batting in Game 1, even though they are the home team. In the previous scene, when Rothstein first arrives to listen to the play-by-play, the announcer reads off the results of Chicago's turn at bat in the top of the first inning.
"The Star-Spangled Banner" wasn't officially America's national anthem until 1931. However, it was sung during the first game of the 1918 World Series, and had been popular for years. It could have been sung before a 1919 game.
Some neighborhood kids listen to the game on a "crystal set" radio. The first "real" radio station in the USA (KDKA, Pittsburgh, Pennsylvania) started in 1920, but smaller broadcasters were on the air as early as 1909. An enthusiastic local could have broadcast details of the game.