Combo fountain pen/pencil from 1930

This green marble combo fountain pen/pencil from 1930 is really good looking and would be fun to draw with if I only would be able to figure out how to refill pen side with ink. I have a wild guess that it should be this little fetus metal clip in the middle, if it pressed it will squeeze the sock. Didn't try it yet. Poly Prep is behind it.

Done