Regarding the Pearl River Bridge brand soy sauce, they might have improved their labels recently, but for a long time you had to read them very carefully. In case you come across some older bottles, here's the scoop:
The label reads:
"Superior Soy Sauce" = regular (thin) soy
"Soy, Superior Sauce" = black or dark soy (it's sweeter and slightly thicker)
With all this discussion, I sure am getting hungry for duck!
Rita