Factual error: At the conclusion of a car chase, in the beginning of the movie, one of the cars is shown going into the river, with the New York skyline in the background. Most prominent are the Twin Towers of the World Trade Center. Since the chase took place in the 20's, theres no way the Towers should have been there.
Visible crew/equipment: At the very beginning, just after the flowers are delivered, a boom mike drops in from the top of the screen.
Factual error: After killing rival mob members in the 1930s, Bronson is driving away in a 20s vintage car. When the scene cuts to a head on view of the getaway car that Bronson is driving, a 1960's vintage vehicle he's on his immediate left, and 60s or 70s vintage vehicles are parked on the opposite sides of the street.