This might be a strange quesiton, but I'll be working on the exterior fiberglass soon and wondered how you can tell if your trailer has been painted? The surface is very dull, but I don't know for sure. I don't see any peeling like paint.
If it doesn't appear to be painted , it probably isn't.
Look in the door jamb, or peel back a little of the skirt trim.
Check for things like window frames, gaskets, or trim with paint on them.
During daylight, look from the inside of the trailer at any exposed shell, that will be the best tell. Gelcoat lets a lot more light
through than paint.
Gelcoat commonly dulls over time, in spite of efforts to keep it shiny.Those who have kept their Eggs shiny have done so by restricting sun exposure and heroic and diligent efforts with polish and wax. They deserve accolades.