The original printing of SR4A was released around August of 2009 - it can be identified by the copyright on the credits page at the end of the table of contents saying "copyright 2005-2009 WizKids Inc."
There is also a printing of SR4A, which I believe is only the 2nd printing and am sure is currently the most recent, released near the beginning of this year - it can be identified by the copyright on the credits page at the end of the table of contents saying "copyright 2005-2012 The Topps Company, Inc."
Apparently, a decision was made to simply update the copyright date rather than do that and also add in a mention that says "2nd printing"