Hello!
That specific aluminium mill was state owned! :D
But more seriously - I heard the American jets were made of duraluminium plated with a thin layer of pure aluminium, that could, and ofte would be polished to high gloss. The German and later Russian aircraft didn't have that thin aluminium coating, and so even if you polished them, you wouldn't get a surface this glossy!
Now somebody has to posta a photo of a recent MiG here! Have a nice day
Paweł