Eagle Flash

The Eagle Flash self filling fountain pen predates the Sheaffer lever filler. Pulling the end knob causes an internal lever to pivot and compress the sac. It also can stay in that position unassisted. Next, place nib in ink. Depress knob to release pressure on the sac and the pen “fills in a flash.”

The filling mechanism is shown unscrewed from the end of the barrel. It is a long pressure bar that pivots against the sac when the knob is pulled. It will hold that position until you press the knob in.