The production was so small and had so little money that Jeanne Moreau was often called upon to lend her Rolls Royce for ferrying around props. She even did some of the catering, particularly in the scenes where Jim visits Jules and Catherine in Germany.
One of the earliest foreign films to be distributed in the US by two Harvard students, Cyrus Harvey and Brian Halliday, under their newly formed company, Janus Films. Janus went on to distribute all sorts of classic foreign films and is now owned by Criterion.
The trivia item below may give away important plot points.
"Sabine", the child of Catherine and Jules, was a boy in real life. His name was Stéphane Hessel, a famous French (German-born) left-wing diplomat and intellectual. His book "Indignez-vous!" (2010), written shortly before his death, inspired several protest movements in the Western world, for instance "Occupy Wall Street".