One of the car can't start but the starter is working fine. Therefore the battery is good. They succeed in starting the car by pushing it but this method can only be used when the battery is dead. Otherwise, it won't start anyway as the problem is elsewhere.
One of the Citroën cars has an oval F plate, meaning the country where the car is registered is France. These country plates rarely appeared before 1949, when a Geneva convention instituted them. They were usually in metal. Plastic ones, as in the movie, appeared in the 1960s.
Lorsque Lucie Aubrac reçoit une lettre d'invitation du libraire Paul Lardanchet, codétenu de Raymond, l'enveloppe est autocollante et de format inusité pendant la guerre.