In the second part, Les Thenardier, when Jean Servais overhears the pair plotting to rob Valjean, Raymond Bernard can be heard softly directing him to leave the room ("Vite!").
In the First Part, after Fantine meets Felix at the dance, a shot of the cards advertising the dance blow one by one off of a table, until they are all gone. Driven through the top of the table can be seen the heads of flathead metal wood screws, which were not invented until the middle 19th Century, or decades after the story takes place.