What is Conklin's Self-Filling Fountain Pen?

In a recent post, we shared an ad about the Conklin Self-Filling fountain pen. It was a celebrity endorsed ad, in a somewhat comical way, where Mrs. Grover Cleveland suggests that self-filler pens would have greater sales if the filling mechanism was better known. The logic made sense  -- the Self-Filler is a lot easier to use and carry with you than an eyedropper-fill pen. How did the Conklin Self-Filling fountain pen actually work? Pretty simply, and Conklin emphasized in their advertising that the self-filling pens were easier to fill than eyedropper filler pens (the common filling mechanism at the time). No extra tools were necessary to fill the pen (such as an eyedropper), hence "self-filler."  Turn the lock ring so its open side lines up with the metal crescent, depress the crescent to evacuate the sac, let go and the ink is drawn up into the pen.  Conklin liked to also point out that it would clean itself through flushing the inkflow system using the same steps. These "Self-Fillers" also excelled in that they did not leak like eyedropper-filled pens tended to. No bumps or ink burps from the joints or into the cap.