After Maranzano's death, when Valachi is offered a hideout in the attic, during the conversation between him and the mother of the deceased, the window down the middle is seen to be a shade of black, but the next scene you find that there is daylight gleaming through it.
When the doctor/medic arrives after Valachi's suicide attempt you can see the TV-Set in the background fully intact. Prior to his attempted suicide , Valachi smashed it with a chair.
Joe Valachi (Charles Bronson) becomes a made man in the Mafia in a scene dated November 5th, 1930, but a subsequent scene when his sponsor Gaetano Reina is murdered, is dated February 26th of the same year.
The closing narration states that Vito Genovese died six months earlier than Joe Valachi. In fact, Genovese predeceased Valachi by more than two years.
At his first interrogation, Valachi states his date of birth as 1903. Valachi was born in 1904.
Jill Ireland portrayed Valachi's wife, Maria Reina Valachi. However, Joseph Valachi's wife's first name was actually Carmela, whom he often called by her nickname, "Millie."
In the movie, Bender had Gap emasculated. In real life, Gap was murdered but not mutilated.
In the scene where there was a possible hit on Maranzanno and Luciano the hit crew escapes in a car from the late 1920s.....but in the back ground you can see cars parked and cars going by made in the 60s early 70s'
Early in the film Valachi is walking around the prison yard and a graphic on screen says it June 1962 but he is wearing a heavy coat.
A couple of times at the start of the movie, in the shower scene, it is clear that Charles Bronson is wearing an orange bathing suit.
At 27:07 during the getaway from the hit a 1965 Ford Fairlane can clearly be seen next to the Packard.
During the chase scene which takes place during the 1920s in New York, a car goes into the river and in the background the twin towers of the World Trade Center under construction can be clearly seen. This is one of the most famous period reconstruction mistakes in film history.
As Valachi drives during his first job in 1930, a 1960s Ford is in the left lane next to him.
About 35 minutes into the movie, at the "Bronx Parish" where a crowd plays a game similar to bingo, the US flag on the podium has 50 stars instead of the 48 stars of that period.
During a car chase scene, the cameras back out too far from the antique cars, and you can see modern (circa late 60's - early 70's)cars in the street with them.
In the 1929 car chase scene at night there are a couple times that the cars drive by windows or open garage doors and it is bright daylight outside of the garage that they are driving in.