In the film, George Zucco differentiates the two characters by wearing glasses for the good doctor, and none for the evil one. Apart from when he forgets - most notably when, as the good doctor, he bends over not wearing any glasses, but when he stands up again (different cut) he suddenly is wearing them again.
When Zolarr removes the coffin lid each time, it is a full-length single piece. When Kate finds the coffin, the lid has been cut in two - probably to make it easier for her to remove.
A single bell is shown pealing, but part of the Westminster Chimes is what is heard - and none of the notes match when the bell is ringing.