Visible crew/equipment: In the scene near the beginning of the film, when the 2 brothers are fixing to leave to join the army. After the mother gives them the flag, the shot changes to the 2 brothers. You can see the boom mic and the camera in the reflection of their shiny brass buckles.
Revealing mistake: In the Fredericksburg battle scene, just after the Union officer orders the men to fall back, there is a 1 or 2 second close-up shot of a Confederate soldier taking a hit and falling back. As he does, a modern wristwatch is visible on his left wrist under the sleeve of his coat.
Trivia: General Robert E. Lee was shown throughout the movie as wearing the three star insignia of a Colonel, rather than the three stars surrounded by a wreath as was the proper insignia for all Confederate generals. General Lee actually wore this throughout most if not all of the war, and this is accurate.