Factual error: When Johnny Depp and Al Pacino are driving in the car (I believe it's the first time Depp drives Pacino around), they pass an MCI billboard - the one that continually updates the figures as to how much money you'd save if you had MCI long distance phone service. MCI didn't exist in 1978.
Factual error: A group of guys are walking into a hangar at some airport. When they are walking into the door you can see a jet moving behind them. It is a Continental Airlines jet with their new Continental logo on the tail. I believe they updated it in the last two years. The movie was set in 1978 and this logo obviously wasn't on the jets back then.
Factual error: In the airport scene, the Burlington Air Express plane being towed is marked Burlington Northern Air Freight, Inc. (BNAFI), a subsidiary of Burlington Northern Railroad. In 1982, BNAFI was acquired by the Pittston Company, which later became Brink's. In 1986, BNAFI changed its name to Burlington Air Express, which is outside of the movie's time frame of 1976-1982.
Factual error: In the beginning of the movie when Lefty asks Donnie if he is Don the Jeweler, Donnie turns to the man behind the bar. On the bar shelf there is a bottle of Absolut Vodka. The movie was set in 1978, and Absolut Vodka was first launched in 1979. The design of the actual bottle in the scene was launched even later.
Factual error: In the scene where Depp visits Pacino at home during Christmas, Pacino is watching TV. On Pacino's TV stand are VHS tapes, including some movies that where not made until after 1978, when this film is set: Death Wish 2, After The Fall Of New York, House, Low Blow, Ghoulies and The Last Dragon.