Of course, "stuffing the ballot box" in various ways has been done since people began voting.
This picture was taken in November 1928. It's of an old voting machine in Los Angeles.
Upton Sinclair's name is printed as a potential elector for the Socialist party candidate for President. Hopefully, if you click on the picture you'll get a big enough version to see that.
Basically, the big handle closed the curtain. The handles to the left could be pulled for a straight-party ticket--all Republican, for example. Otherwise, each candidate had a handle, and propositions had handles that moved to "Yes/No" positions.
That site says that all equipment must have a paper trail. With the Inka-Vote system, it's all paper in the precincts, with the exception of the machines for the handicapped--which often don't work, btw.
What sort of clue or irregularity would lead to an actual audit of that paper trail?