At around the 55 minute mark in the bar room fight scene, the differences between Fred MacMurray and his stunt double can be clearly seen.
When Purdy gets tangled in the "barbed wire" from the fence, it is obvious that it is not metal wire, but thin rope made to look like barbed wire.
The henchman Larsen/Kincaid kills on the roof is hanging down inside the roof hole but never drops the pistol.
In the climactic scene, when the damaged player piano runs down, its pitch slides downward, like a tape recording slowing down. Indeed, electric player pianos didn't exist until the 20th century, anyway - the early ones were all treadle-operated.
When Jim meets up with Ellen at her buggy after the dance, tire tracks from modern vehicles can be seen on the ground.
As Mark rides off to cut Williams fence there's obvious mismatch in the audio that was looped/ADR/dubbed. "MARK!" was recorded on location but the following, "Do you know how to use a gun?" noticeably not.
Then shortly after other dialog was cut mid sentence. "But I'll give you some good advice" being location audio and the rest of the sentence, "don't let Williams set the time... way you can." being looped / studio audio.
The tone of voice changes but also note the absence (disappears between looped cuts) or its inconsistency as it relates to location (background) ambiance.
[Tip for filmmakers: ALWAYS record a stretch of location audio in case some dialog has to be rerecorded in the sound booth. The viewer expects the 'background noise' to be consistent between cuts of two people talking, which it isn't in this case.]
Then shortly after other dialog was cut mid sentence. "But I'll give you some good advice" being location audio and the rest of the sentence, "don't let Williams set the time... way you can." being looped / studio audio.
The tone of voice changes but also note the absence (disappears between looped cuts) or its inconsistency as it relates to location (background) ambiance.
[Tip for filmmakers: ALWAYS record a stretch of location audio in case some dialog has to be rerecorded in the sound booth. The viewer expects the 'background noise' to be consistent between cuts of two people talking, which it isn't in this case.]