Waterman's 12

This Waterman's 12 is a hard rubber eyedropper filler with 2 gold filigree bands on the barrel for added aesthetic. To fill the pen, you'd need to unscrew the nib unit and load the ink via an eyedropper. This model features a cone cap which holds onto the barrel via friction. Often these caps are split at the base due to excessive force of someone wrenching the cap on too hard. Luckily this one still works and is crack-free!

From the Waterman's 1908 catalog, here are 4 variants of the No. 12 style of pen. The pen I own is the one second from the left.