A customer is disputing the size of the type we used in a brochure claiming the type is too small and not 12-point. What are the character height tolerances for different point size fonts?

Font size is NOT a measure of the height of the font character. Font point size comes from the measure of the thickness of the old lead hand set type, not the size of the actual character. The size of the metal type characters were smaller than the full width of the metal type or point size. The font character height could be 50% the thickness of the metal type or point size or about half the height of a type character in a different font of the same point size. Adobe and individual font software manufactures may have a standard or guideline for font size and type character height for their digital fonts, but again not all font characters are the exact same size in a given point size. You should be providing the customer some type of proof, even a laser copy, so the customer can see the layout and text before the job is printed.