There may have been revisions to the design, because the knob on my Frontline controller is molded right on the shaft. There is no roll pin, set screw, nothing. If your controller is like mine, then it is a little bit of work to disassemble the controller to take the shaft out. I'd bet that the roll pin was added later, because it makes for a rather poor design without it. Possibly Taito had more than one supplier for this controller, as well, and that may explain the difference.
