The full form of ICGS is Independent Coin Grading Service.

ICG guarantees that all coins submitted to its grading service will be handled with the highest standards of professionalism and integrity. In addition, all U.S. and Foreign coins graded and encapsulated by ICG are guaranteed to be genuine, unless they are encapsulated in the ICG Educational Slab. Any Customer may resubmit any coin for review of the grade assigned by ICG if such Customer believes that such coin has been over-graded by ICG. If the coin submitted for review by the Customer receives a lower grade under ICG’s internal review practices than the grade originally assigned, ICG shall, at ICG’s option, either (a) replace the coin, or (b) pay any difference between the current fair market value of such coin at the newly established grade and the current market value of the grade originally assigned to such coin. The fair market value shall be determined solely by ICG. From time to time, ICG will receive certain Pedigree Coins, Important Rarities, large quantities of coins, bulk submissions, or coins where the identity of the owner has been well publicized or well known throughout the numismatic community. Although ICG may be able to assume the identity of such owners, ICG reserves the right to grade such coins under ICG’s standard practices. This ICG Guarantee shall not apply to:

(a) any clerical error with respect to the description or grade of the coin;
(b) any coins subjected to improper storage conditions (such as extreme temperature or extreme conditions etc.);
(c) any coins exhibiting environmental deterioration subsequent to certification; that is, after ICG has graded and encapsulated a coin.  This deterioration may include, but is not limited to, spotting, hazing, PVC contamination, changes in color, and corrosion;
(d) any copper coins because the color and surfaces can change due to environmental factors, including weather and improper storage; ICG does not guarantee against changes in the color of copper coins, or against copper spotting subsequent to grading and encapsulation by ICG;
(e)  any coins not encapsulated by ICG.

ICG cannot guarantee the liquidity of any coin graded by ICG. ICG certification of a particular coin cannot provide protection from the risks inherent in any market for such coins, if such a market exists.