I don't collect those, but "no denomination" rings a bell here. From http://en.wikipedia.org/wiki/Chinese_Silver_Panda : "In 2006, a flood of counterfeit 1-ounce silver pandas came onto the market (...) Many of these were easily distinguishable from the real thing by the lack of a denomination, which all authentic legal tender silver Panda coins have." Christian
If it's supposed to be one ounce of pure silver, it should weigh 1 troy ounce, which is about 31.1 grams.