This passage discusses coin collecting and how to grade coins. It explains that coin grading is important because a coin's value depends on both its popularity and scarcity as well as its condition. The passage outlines the standardized grading system for coins using letter designations from MS (mint state) to G (good) along with number grades within each category. MS coins can receive grades from 60 to 70, with 70 being the highest, perfect condition. The passage explains the characteristics graders examine for each number grade, such as contact marks and luster. Coin collectors prefer coins that have not been artificially cleaned, as cleaning reduces value.