Upside-down letters?

While looking through Marks' Standard Handbook for Mechanical Engineers for something entirely unrelated to this thread topic, I came across a list of proofreaders' symbols. One of the corrections, shaped like a '9,' means "turn letter" i.e. "The letter is upside-down. Fix it." OK, I can make an effort to write or type an inverted letter intentionally (turn the paper upside-down or make a special effort to write the letter that way). AFAIK, there is no way to do this in Word; even if there is, it requires some special effort. My question: Is there any way to accidentally create an upside-down letter on any typewriter or typesetting machine that's ever existed, i.e. is the existance of the "turn letter" symbol warranted?

Strainger:

Consider the loose letters used in old-time printing presses. Each individual letter was moulded from lead and kept in a compartmentalized bin or "printer's box." You are not looking at the art with enough historical perspective. :)

A-HA! Thanks, Dr. F.!