I just bought a used gold C-3PO (not the 14k version, but the 10,000-made version). There are some places under the arms and on the right foot where there is no gold paint. I think that they are all like this, but I'm not sure. I'm looking for someone to verify that I didn't just get taken to the cleaners. I can still open an eBay case if I need to.
Yes, that sounds like the genuine article - LEGO was unable to chrome each part separately, so there are bare spots where you describe. Only the customs will have been made up of individually chromed parts.
Yes, I have an original chrome gold CP30 and mine also has those bare spots. Like mentioned earlier, LEGO painted these units as a whole and not separately... so that's what's essentially makes them legit, and the bare spots are all the same on the originals. I have done research on it after I realized that's what I had was the worth a pretty penny haha
Don't worry my friend, those "unchromed" spots are because of the regular use of that minifigure.