ASCII has a limited number of characters, so they designed it so some do double-duty. The grave could be a grace accent if you backspaced over a letter, or it could be an opening quote mark. The apostrophe was the reverse: it could be the acute accent. The fonts were drawn so these characters were angled enough to be accents, but also looked like quote marks. The apostrophe wasn't a vertical prime sign. Angle brackets and greater/lesser-than also double-up.