Bill Maher -- A CelebriGum Rarity

Even if you're not a stamp collector, you've probably heard of the famous misprinted 1918 airmail stamp:

Only one sheet of 100 upside-down airplane stamps was released; single stamps from this set now fetch close to a million dollars.

So I expect well-heeled CelebriGum fans will be driven into a frenzy by this remarkable one-of-a-kind photo of Bill Maher:

Christie's pre-sale estimate is $3.5 million. 

(Not the auction house; New Jersey Governor Chris Christie, who's notoriously bad at guessing the value of upside-down pictures.)