Numismatic Guaranty Corporation. NGC is the world’s largest independent grading service, having already appraised more than 31 million coins. Over the last 28 years, NGC has graded the majority of the world’s most significant coins and collections, including the coins at the Smithsonian Institution, the National Museum of the United States, and the Shanghai Mint Museum.
Each coin graded by the NGC is furnished with a certificate of authenticity recognized the world over.