Wirt's Hump filler

Here is a small treasure, a Paul Wirt Hump filler. In the early 1900's several pen makers used a hump, bump or screw to deflate / inflate a rubber sac to fill and flush a pen with ink.

Most notably was the Conklin Cresent Filler, but Parker had a hump filler also, as did Welty and many others.