Certified coins are coins that have been evaluated and graded by a professional grading service. These services assess the coin's condition, authenticity, and overall quality, assigning it a grade on a standardized scale. This process helps collectors and investors understand the value of the coin and ensures that they are purchasing genuine items. Once graded, certified coins are often placed in protective holders, which display the grade and other relevant information. This certification adds credibility and can enhance the coin's market value. Popular grading services include Professional Coin Grading Service (PCGS) and Numismatic Guaranty Corporation (NGC).