The third bite in your picture is not easy to see, but is there! the top lever actually slides over the small notch in the rib extension. A true "HIDDEN THIRD FASTENER" is a rib extension, AH LA H&H, where the rib extends through the extractor into a hidden recess in the breach face! I find the doll's head to be the better of the two types. The best being the dolls head with a bite in it's back side AH LA WESTLEY RICHARDS. This type really has four fasteners! The one shown in you pictures has four as well!