Without his "toupee", the line where Walter's false bald scalp joins his own skin at his forehead and temples is obvious and poorly applied by the makeup artist.
Noreen's husband's corpse is seen to be breathing when the police take his wallet to find out his identity.
False beards are generally attached to the face using either spirit gum or rubber latex, both of which have a distinctive odor, which would be readily apparent to anyone in close proximity to the wearer - such as when Noreen kisses the disguised Walter Mills on the mouth.
Walter Mills discards his glasses when he is in the guise of Philip Marshall and seems to see perfectly well without them.