This has been a very interesting thread, and a great chance for some to learn about something they knew knothing about.
There is some good information in Jeff Lilly's book. "How to Restore Metal Auto trim".
In his book he states that GM SS trim has been flash chromed since 1957 ! I believe it to. They also use a 57 Chevy wheel cover as a test piece, and go into detail on how to remove the flash chrome layer using a muratic acid solution.
As stated in this thread already, when you break through the flash chrome there appearance of the two finishes is drastic.
I have had limited success with GM SS trim when I remove all the FC. I have found that the base metal is not of very good quality, sometimes even porous, and it flat will not come up to a nice bright luster no matter what you do.
A few years back I polished some 64-65 Dodge trim that was not flash Chromed. It looked like jewelery when finished. I could tell there was a big difference in the quality of the sheet stock used ?
On very nice used trim with little or no deep scratches you can get away with some wet sanding, 1000- 2000 grit.
If you ever do this you will notice the chrome is very hard and progress is slow, and for you guys that get it, as you cut into the base metal, it is like sanding filler compared to the FC on top.
Allot of trim I see has been damaged from handling after it has been removed from a car. I like to bundel it up with tape to keep it from banding together.
I carry a piece of Camaro trim with me to cruise nights that has half the FC sanded off. Used it several times to prove a point.