I would say the one in LiAm84's example IS gold plated. The gold will show tarnish like that if it's thin. Over a long period of time the underlying silver can tarnish and show this effect. Anyway, only metal tarnishes, and that definitely isn't what brass tarnish/corrosion looks like under lacquer.
The other thing I see is tiny micro scratches. You see that on gold and silver plate but not, in the same way, on lacquer.
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