But the cotter pin was missing?

Cotter is a city in Baxter County, Arkansas, United States.

He asks, Might not the cotter pin have been defective?

It had been disconnected and the cotter pin had been removed.

and is coupled to the bell crank here by a cotter pin.

Is it improper to ask if maybe this cotter pin mightn't have been defective?

Mr. Miller, would you be willing to stake your life on there being only one defective cotter pin in a million?

If it had, you'd expect to see a part of the shearedoff cotter pin in one of the holes, or scratches or marks or some bending to show where it had pulled out.

But if I were to remove this cotter pin and uncouple this shifting rod, a very simple operation, as you can see, then no matter what you do with the shift lever, the bell crank remains as it was,