Matthias Schoenaerts was cast after starring opposite Marion Cotillard (director Guillaume Canet's wife) in Rust and Bone (2012). Canet has said that he chose Schoenaerts after hearing Cotillard praising his acting several times. Schoenaerts and Canet met briefly on the set of "Rust and Bone", when Canet came to visit his wife.
The armored truck robbery takes place around New Year's, but a poster from "Chinatown" is on the side of the bank. That picture opened in June, so there's no way it would still be displayed nearly seven months later.
The story opens in 1974 but the song playing in the background on the record player is "New York Groove" from Ace Frehley's 1978 solo release and even the original by the band Hello was not released until 1975.
The armored truck in the movie has LED-type tail and reverse lights. These lights became standard during the 2000s and did not exist in the 1970s, when the events in the movie happen.
Frank: [Frank & Valenti are on a stakeout. Valenti slurps the last of his drink and tosses the cup into the back seat]
You do understand that this is my car, not yours, right?
Leon: [to his son, Frank]
Listen, your mother... your mother was a bitch. She was a real bitch. She beat the shit out of your brother and sister on a daily basis with whatever she had in her hand. She was a violent drunk, she was a twisted fucking slut.