Let's do a quick sub-teardown of the latching mechanism that is the little white pin. In the pic above, looking down, the pin is just to the right of 6 o'clock. The pin has a spring that pushes it up. When the tab is pressed down, it in turn presses against and frees a little plastic latch that seesaws up to allow the inner slip ring to rotate.
Here we see the tab in its default up position.
Last edited by beermeister kink; 01-29-2013 at 10:02 AM.