Wonder Where Those Came From?

[trdsf]

So apparently there's an up side to moving: not only did I find a long-missing Esterbrook, but three more pens surfaced: a Berol Fontaine, a transparent green Sheaffer Student, and a crow quill with a brass ferrule and nib mounted thereon.

 

Anyone know if someone's sorted out a way to refill the Fontaine? It was supposed to be disposable, but I can't realistically bring myself to actually throw a fountain pen away... Anyway, I managed to prise the end cap off, and it looks like there's a cartridge of some sort in there, but I can't tell if it's affixed on the business end or not.