That is a very nice frame, I would love to have it.
I don't think they chromed that frame, both my Pinarello and Guerciotti are fully chromed I do believe, under the paint. The paint on both is lacquer. Lacquer becomes brittle but it has a lovely deep transparency that is made more brilliant by the chrome or white base coat underneath. Unfortunately it is brittle and easily damaged. The same effect can be achieved with two part modern paints by building over a white base, adding clear to the second and more clear to the third coat and then finally after decal application, clear. Two part acrylic laquer can be finished beautifully this way.
The top tube is more rusted because that is where the sweat landed. In a way, if you could clean it up, buff it with some carnuba wax and get the shine back, leave it be, as a badge of honor from the ghosts of past riders, unless it is pitting rust, which needs to be addressed.
This one was done by Ten Speed, a little better paint in that it is somewhat more durable:
