From their website: http://www.cgccomics.com/about/ "Comics Guaranty, LLC (CGC) is an independent member of the Certified Collectibles Group of companies. The Certified Collectibles Group is an umbrella organization consisting of Numismatic Guaranty Corporation of America (NGC) the leading grading service in rare coins, Sportscard Guaranty, LLC (SGC) the fastest growing grading service in sportscards, and now CGC the first independent, impartial, expert third party grading service in comics. Our certification companies have a proven and respected commitment to integrity, accuracy, consistency and impartiality in grading collectibles that has made them leaders in their fields. This proven model of success is ideally suited to adapt to the unique challenges of grading comic books." It's a generally accepted comic book grading service, and thus the price of a CGC graded comic book is generally higher than a normal price guide (Beckett, Overstreet, etc.) A collector sends their comic book for grading, gets reviewed, and then place in a tamper-proof sheet and sent back to the collector. More info: http://www.cgccomics.com/faqs.htm