In this film, Richard of Gloucester, also known as Richard III (played by Vincent Price), kills Mistress Shore (played by 23-year-old Sandra Knight) on the torture Rack. This changes history. In real life, Mistress Shore (1445 -1527) lived to be 82 years old. And if she would have died at age 23, she would never have lived to become the mistress of King Edward IV of England, and the mistress of other noblemen, including Edward's stepson, Thomas Grey (1st Marquess of Dorset), and William Hastings (1st Baron Hastings).
When Richard pushes the freshly murdered Clarence into the vat, you can see Clarence take a deep breath and hold it, just prior to being submerged.
As Richard bends down to kiss the forehead of King Edward, who was dead his bed, you can see King Edward squinting both of his eyes slightly.
When Price falls off his horse near the end of the film, the camera is much too close--the face of his stunt double is clearly visible.
Just after Richard throws the ax through the stained glass window, you can see the shadow of the camera crane on the floor, rising higher and higher and pulling back.