When Ralph meets Margie in the library, all the shelves between them seem to be full of books from end to end, but each time Ralph removes one book, he has an unobstructed view of Margie on the other side.
In 1927, a flatbed truck advertising a political candidate is blaring marching band music from PA speakers. A 78 rpm phonograph or any other playback device then existent would skip or otherwise be disrupted by the truck hitting bumps and turning corners. Back then, candidates who wanted music hired small bands to play on the trucks. Clearly the music was added in post production.
In one scene in her bedroom, Margie turned on her radio. It immediately came on. In that era, radios had tubes, not transistors. The tubes had to warm up before the radio came on.
The hairstyles of Jeanne Crain, Barbara Lawrence, and Lynn Bari are strictly 1946, although the story takes place in 1928.
Although the featured automobiles are of the proper vintage, newer models can be seen in the background on several occasions.