Grading Colonial Spanish Silver Coins (Conception Shipwreck) Professional grading services such as the Numismatic Guaranty Company (NGC) and the Professional Coin Grading Service (PCGS) assign grades using trained specialists who examine coins under controlled lighting and magnification. They evaluate strike sharpness, the coin’s original mint luster, the number and placement of abrasions from handling or bag contact, any impairments such as cleaning, and overall aesthetic quality. Some coins ma