In the overview shot of San Quentin, smoke is pouring out of a smokestack on the right when it suddenly, completely disappears in the last second of the shot.
While she waits for her co-conspirators to break through the wall into her cell, Nan is shown starting the gramophone twice.
When Linda meets Nan, they stroll down a path through the prison yard. It's clear that the background of the path is projection footage as there is gusty wind violently whipping a tree and shrubbery around, yet their hair doesn't move.