ALL of the aero-shaped Argosy trailers have one-piece end caps. Most are galvanized steel but it's reported that some were made of fiberglass. No aluminum up there.
A number of people have stripped the paint from their Argosy to polish it up and have usually ended up with contrasting end-caps. I've seen photos of a couple that have been painted silver which is a nice look if done well and that's the color you want.
If the trailer you're looking at looks very good without paint, it should be fine that way. If you'd prefer the classic Argosy look, you can always have it painted.
Il Carriaggio — 1975 Argosy 24 | Il Progetto — 1976 Argosy 28 Center Bath | WBCCI# 15566
He has all of the virtues I dislike and none of the vices I admire. — Sir Winston Churchill