Re: What is the second pin for?

The second pin is an "indicator" that the knuckle lock pin has dropped and the knuckle is locked closed. On a Sharon, Climax or freight Janney, etc., the knuckle lock pin drops and a shoulder of the pin rests on the coupler body. If the pin doesn't completely drop and lock, the shoulder of the pin rests above the coupler body to tell you the coupler has not completely locked. NOtice on a tower the knuckle pin that is exposed and connected to the lift linkage looks like a piece of bent chain, and it would be impossible to tell by looking at it if the pin was all the way down.

More than once I've been "Towered" by one of these couplers if the open knuckle was where I couldn't see the "telltale lever". After making the joint, and pulling on it, the knuckle opened 10 car lengths down the track.

Quite embarassing when the train was blasting off out of town....