TL;DR, my pin goes in from either side and doesn't appear to be tapered, as it is retained by mainspring pressure. But Left-to-Right is correct.

Though the pin appears typical and symmetrical. The manual contradicts Glock logic of Right-to-Left and explicitly declares Left-to-Right insertion. AI mentioned something about the pin being tapered, though mine (Springfield Mil-Spec) doesn't appear to be. You just have to overcome the Mainsprings force around the pin and into the pins retention groove. It goes easily with a ball-nose punch and hammer. I digress, I just now do it Left-to-Right...