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If you look at the negative space, you will see channels instead of triangles. The channels fit the peg built into the main body so that the upper carriage cannot sit between digits when you turn the carriage for handling multiplication.
Without the name of the file I am unsure which pin you refer to. There are a few pins that might be called a crank pin. One is at the bottom of the main shaft which turns the zero positioning disc with the main shaft. One is at the top of the main shaft and holds the crank to the main shaft. One is actually a little screw that has a nub on the end for holding the handle on to the crank while also allowing the handle to spin on the crank.