Have, on occasion found them marked with labels like "RADIO" but to be honest.
Find the primary house fuse block, get a test lamp (This is like an ice pick with a light bulb in the translucent plastic handle and a wire with clip) clip the clip on a known ground and go tap tap on each and every fuse in the box (Tap/probe both ends one at a time)
Dark/Dark fuse unkonwn
LIGHT LIGHT fuse goood
LIGHT dark or dark LIGHT, fuse bad.
In the house block, dark dark should not happen (Does happen on the chassis block though).