Chances are it's supplied by another addon and then shared between addons using SharedMedia.
You can try typing this ingame:
Code:
/run local L = LibStub("LibSharedMedia-3.0") print(L:Fetch("font", "name"))
So if it says "ANTIQUE" in the Chatter font-options, that's what you should put in instead of
name. It's also case-sensitive. If it finds an entry the path will be printed to chat, otherwise it will print
Fonts\\FRIZQT__.TFF which is the default font.