Shortly into the movie while counting the money, two cops knock on the door. The tablecloth with the money is folded up and pushed to the floor. When the cops enter the room the tablecloth, money and briefcase are back on the table.
When Anthony Quinn is beating the man in the chair of the police station, his gun falls out of his holster. It is never put back in.
At the final scene a guy is shot by a sniper from the roof another building across the street. His weapon is a hand gun with a silencer held with both hands. A clean head shot from that distance would be an extreme stroke of luck.
When the police bang on the door asking for the owner of the 1968 Cadillac in the opening scene, the black Caddy that the men were driving was a very distinct 1965 Coupe de Ville. After 1966, the headlights on all Cadillac models were side by side and hidden behind shields when not in use. The car in this scene has over/under headlights with distinctive chrome frames that are unique to 1965 de Villes.
While climbing out of the burning Lincoln while on fire, Burt Young (or at least his stunt double) is clearly wearing protective gloves.
In the bar, D'Salvio punches Henry J in the stomach twice, but there is no sound effect.
About 18 minutes into the movie, a cameraman can clearly be seen in the bathroom mirror.
At 7mins 57secs into the movie a patrolman runs out of an alley and alongside a parked blue station wagon, in a failed attempt to stop the robbers. He clearly has wires trailing from his pants leg and leading behind the car. Most likely they were attached to and used to activate the exploding blood packs hidden under his jacket.
In the prologue when Joe, Jim and Henry are trying to drive away with the drug money, a cameraman is visible in the backseat of the getaway car between shots - capturing shots from inside.
In the final scene, 1:36:10, the chase and shootout is filmed on the rooftops of downtown Manhattan (Chinatown?) while the location is supposed to be 637 Lenox Avenue, in Harlem, above 110th Street.