Pifias

Various French newspapers are shown, in particular Le Monde with the picture of an arrested suspect on the front page.

In fact, Le Monde didn't carry any photos at all until the 1980s, let alone on the front page.

In the final moments of the movie, Maigret passes a bench where a grandfather and his grandson are reading a Tintin comic, however, that version of that comic (see back side of the comic) wasn't published in the 50's.

During scenes where there's flash-photography, modern capacitor driven flashes, with multiple sequential flashes from the same flash-gun occur. At the period the film is set magnesium flashbulbs were the standard, which have to be replaced for every shot. These scenes ought to have had much fumbling trying to remove and replace dead glass bulbs, and been accompanied by loud pops as each flash exposure was made, and the crunch of glass underfoot, as reporters usually just dropped them.

At the end of the movie, Maigret walks through the park where we see an older man and child reading an album of TinTin ("Le Trésor de Rackham le Rouge", first published in 1944). The back-cover of the album shows all the album covers, some of which were not yet published in 1955. More so, that back cover design was not used until the 1970's.

The clothes peg in the drawer appears to be a modern plastic one.

The story is supposedly set in 1955 but one of the street scenes has a black Simca Aronde P60 going by. This model was not released until October 1958.