I have received a dollar bill that is marked “1957” but has the signature “C. Douglas Dillon / Secretary of the Treasury.” This is surely impossible, because Dillon was JFK’s Treasury Secretary, not Eisenhower’s. What is more likely: that this bill is a forgery, or that it was a misprint at the Treasury? (If it turns out that this is a rarity worth millions of dollars, I warn potential burglars that my apartment is protected by a ferocious attack cat.)
UPDATE: Much thanks to all readers who wrote in! It turns out they kept making 1957s long after 1957 . . .