" ... if you are talking about "bullion bars"... 100 mills means a fake electroplated bar. It's basically worthless. In this instance, the word "mills" relates not to the weight, but the thickness of the electroplate. Again, a "mill" is one/1000th (0.001) of an inch.
The so-called "100 mill bullion bars" that you might see on eBay or Overstock.com are nothing less than attempts to RIP OFF THE UNWARY. These "bullion" bars are nothing but copper or other base-metal bars electroplated with anexceedingly thin surface of gold (or silver, as the case may be). To keep these ads "legal," somewhere buried in the verbiage it will say that the bars are base metal electroplated with a micro-thin layer of precious metal.
These bars are NOT WORTH A SINGLE BREATH of your time. If you were to buy one, good luck trying to sell it to anyone. This truly is BUYER BEWARE time."
Read more: http://wiki.answers.com/Q/How_much_money_is_100_mills_worth#ixzz1mIloFsMF