http://en.wikipedia.org/wiki/Question_mark According to the wikipedia article I've linked to above, "qo" was sometimes used in the middle ages to abbreviate the latin word "questio" in the way that we might use a modern day question mark. I can't find any example of this anywhere online. Help?
The Wikipedia article itself says evidence is lacking:
The symbol is also sometimes thought to originate from the Latin quaestiō (that is, qvaestio), meaning "question", which was abbreviated during the Middle Ages to qo. The lowercase q was written above the lowercase o, and this mark was transformed into the modern symbol. However, evidence of the actual use of the Q-over-o notation in medieval manuscripts is lacking; if anything, medieval forms of the upper component seem to be evolving towards the q-shape rather than away from it.
Citation  is a 19th century dictionary:
Brewer, E. C. Dictionary of Phrase and Fable, 1870 (rev. 1894), s.v. 'Punctuation'.
I couldn't find this particular edition, but none of the other 19th century editions I found contained this claim.