Just after Mr. Newman has been attacked, one of the frames on his glasses is obviously bent. However, when he enters Mr. Finkelstein's shop just seconds later, his glasses are in perfect shape.
About halfway through the movie, Larry and Gert are in an automobile. There is a vinyl "Sport Grip Steering Wheel Cover" laced around the steering wheel of the car. It is noticeable due to its distinctive pattern of perforations and cushioning. This item was not in existence in 1944, the year the movie is set in.
When Mr. Finklestein discovers the antisemitic note taped to his store window, it is attached with 3M "invisible/magic" tape developed in the 1970s. During the 1940s, cellophane tape was transparent, not translucent.