"I have a fountain pen."
Translation:J'ai un stylo plume.
It is not that old because I was taught "plume" at school, the derivation of which comes from the time when quill pens were in use (being sharpened feathers dipped into pots of ink). I enquired in an earlier discussion whatever happened to "plume", as I remember the song "La plume de ma tante est dans le bureau de mon oncle, le papier de mon oncle est sur la table de ma tante".
So how do you say quill (pen)? GT got plume d'oie, literally goose feather. Wikipedia just says plume as goose quills are no longer used: https://fr.wikipedia.org/wiki/Plume_(%C3%A9criture) -- they hyphenate stylo-plume, more formally plume de stylographe?