Astoria | Vintage Montblanc Pens is my source of information on this filling system.
The concept appears to be the same as the Turnstile pen.
I am basing my observations on pictures and description from the above website only. I do not own one and I have not personally inspected one.
Pictures show the end of a standard pressure bar protruding from the end of the barrel. On top is a square metal piece topped by a metal rod mounted in the center. It looks like the cartoon version of a dynamite detonator. Inside the barrel end cap is a metal piece with two helical “ramps” that push down on the transverse rod when twisted.
Also seen is a version with the pressure bar button and twist cap reversed. I can’t read the imprint, but the website implies this is a Matador” pen. The square button on the pressure bar has the “ramps” and the transverse bar is mounted inside the cap.
