I read an Article in our local newspaper a few days ago about counterfeit Cisco. This prompted me to Google (I know it's not really a verb right) the topic and a ton of articles are out there. I read a few and it seems that the two most common ways Cisco gear is counterfeited is a 'look-alike' gimmick. Also, another common way seems to be over production with duplicate serial numbers. I found these articles interesting... and maybe you will too.
Here is a picture of the "Andover Test" that I saw out there, and a few points on how to spot a fraud.
Here is the article with the "Andover test"
http://www.andovercg.com/services/cisco-counterfeit-wic-1dsu-t1.shtml