The San Juan Car Company AAR Type-E coupler is one of the most realistic couplers in model railroading regardless of scale. The coupler provided reliable operation when first produced. Somewhere along the way, the die was damaged and repaired. The repair wasn’t exactly right so the operating characteristics of the coupler changed for the worse. A common symptom of the problem is that the coupler won’t drop the lift pin when the knuckle is closed. A sticking lift pin prevents the coupler from locking so switching is made more difficult. The revised coupler can be spotted easily by looking at the rectangular slot on the bottom of the coupler body. This is the slot where the lifting pin moves up and down. The opening was enlarged when the die was repaired. This created slop in the pin movement making the uncoupling balky. Study the close-up photo of the two coupler sprues. The darker one is an older version with a thicker back wall on the opening. The coupler on top has a very thin back wall.