It's not the exact same thing, but just look at museum Skyraiders vs. pictures of operational ones. Real Skyraiders seemed to have a lot of smoke and dirt on them, with a flatter overall appearance, while most of the museum planes I've seen look shiny and factory mint. I'm sure that's true for just about any aircraft, regardless of period or origin.
Some of the 109 pictures I've seen do seem to show reflective surfaces, though I wouldn't necessarily call them shiny. It's looks more like what I would call a satin finish.