With these sorts of stamps, if you are going too fast, and don't ensure that you've stamped the full letter/character, then it's possible to get only a partial stamping, even if the full stamp letter is present.. it might be interesting, and prove/disprove the point if someone who has a 'B' stamp, tries to stamp it 'not squarely' and see if you can produce an upside down/reversed 'P'....