In the train one of the resistance members open the pocket watch with QUARTZ inscription on dial. Second hand of the watch moves in distinct steps reaffirming they have a quartz movement inside. Quartz watch was not invented in 20s and was not available till late 60s.
In one scene a recording by Louis Armstrong is heard playing. In 1923 Armstrong was not even a solo recording artist yet (he was still a sideman in another man's band), and the recording that's playing is clearly stylistically from the 1950s or early 1960s.