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Well I took a close look at both couplers on C&NW caboose #11142.  Both couplers had knuckle pivot pins with no cotter pin retainer to retain them against upward pullout.  The following observations apply to both couplers:With the knuckle closed and locked, it was lose enough that I could wiggle it around and find a position where I could freely lift the pivot pin.  If I then lifted the pivot pin six inches and let it go, it would drop all the way back down until its head bottomed out.If I repeated lifting and letting go of the pivot pin, and pulled out on the closed and locked knuckle as the pivot pin was falling, the knuckle pin bore would grab the pin and stop it in mid drop.  If I let the pin drop back down to normal position, and pulled out on the knuckle, I could see that it made contact with the pivot pin as that pin moved slightly to the left.  And when the pin moved in response to pulling out on the closed and locked knuckle, I could not move the pivot pin.Then I pulled the pivot pin completely out and pulled out on the closed and locked knuckle.  The knuckle shifted slightly to the left and stopped as the force bearing ridges near the knuckle pin came into contact.  It appears as though those ridges would carry the load and keep the knuckle in its closed and locked position with the pivot pin missing.When pulling out on the closed and locked knuckle and looking down the open bore for the pivot pin with that pin removed, I saw that the bore of the knuckle and the upper hinge bore of the coupler housing were not concentric.  The two bores were misaligned with the knuckle bore about 1/8" too far to the left.  The pivot pin could not be passed down through these misaligned bores.From these observations, in the case of both of these couplers, I conclude the following:1)   When a pulling load is applied to the closed and locked knuckle, it shifts to the left and bears against the pivot pin, transferring a substantial portion of the pulling force to the pivot pin as a shear load.  2)   If the pivot pin were missing, under the same load pulling circumstances, the knuckle would remain in the proper position, shift to the left, and transfer its loading against the force bearing ridges near the knuckle pin bores.
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