A coin collection must be given proper care to maintain its value and luster. While you might be inclined to clean your coins from time to time, cleaning can actually cause damage and lower their value. But if you do insist on cleaning your coins, only use mild soap and water—no chemical cleaners—and dry them softly without brushing.
Only handle your coins around the edges, between your thumb and index finger. Never touch the surface on either side, because that could leave corrosive fingerprints and oils that might lower a coin's value over time. Better yet, consider wearing gloves when you handle your coins. To protect your coins from falling on the floor, only hold them over a soft surface. Furthermore, never hold coins too close to anything that discharges liquid.
If you're looking to have your coin collection graded for value, bring them to Coins of the Realm in Gaithersburg, MD. We have been grading coins, gold, stamps, and jewelry for collectors in the area since 1974, and you can learn more about our services by calling (301) 637-4390.