Comics Guaranty

Prior to advent of grading and authentication services, both buyers and sellers were vulnerable to misrepresentation in the marketplace. Seller could benefit from overstating the quality of a book's condition to inflate the price, while a buyer could dispute the condition of a book with the intention of purchasing at a lower price. While reputation scores in online marketplaces can disincentivize repeat offenders by lowering their scores, collectors lacked a reliable, low effort way to ensure a comic book being sold matches the listing's stated quality. Grading services aim to provide consistent, objective grading and authentication, which can mitigate the risk of misrepresentation otherwise inherent with comic book collecting.

Grading

Condition is a significant factor in the valuation of a comic book. An example is Action Comics #1, the first published appearance of Superman. In 2010, two copies sold on the comic book auction website comicconnect.com for record prices. One copy was CGC graded 8.0 and sold for US$1 million. The second book at a later auction, a copy CGC graded at 8.5 sold for a record-setting $1.5 million, the most ever paid up to that time for a comic book. A 9.0-rated version sold at a 2014 auction for $3.2 million. This underscores CGC's ability to provide a grading service as a neutral third party from a transaction, this created a degree of impartiality that did not exist before. This has shown that there is a demand for graded books as consistently these books have set sales records.

Signatures

CGCs gold label Signature Series is a signature validation service in which a CGC representative witnesses a comic being signed by a specific individual as requested by the comic book's owner. Furthermore, the CGC establishes a chain of custody of that specific comic until it is “slabbed” and subsequently returned to the individual who ordered the signature series grading and verification. This mitigates signature forgery concerns.

Identifying restoration and counterfeits

For highly valued comics, a higher grade can result in a price difference of thousands of dollars. Similarly, a comic book marked by CGC with the purple "Restored" label can suffer a significant price reduction.