NGC and PCGS certified coins are the best way to invest safely in coins. They keep the coin safe and secure, and their certified grade is always guaranteed. It's tough to keep them scratch-free, especially when exhibiting them or bringing them to trade shows, etc. On my better coins, I use a soft plastic sleeve to protect the surfaces of the slab. I have found the baseball card sleeve made for "vintage" cards are the best size, made by Ultra Trading. Just use the search words  "ultra" and "vintage", and several should come up. They sell for a few cents apiece, in packs of 100, and are a great investment to keep your slabs nice. Short of getting your scratched coins re-holdered, sometimes a time-consuming experience, there is another way...There is a polish sold for plastic, available in hardware stores, that will minimize the hairlines on the surfaces of the holder....this really works!  PLEASE MARK THIS GUIDE HELPFUL, IF IT WAS......THANKS!

UPDATE! NGC has come up with a coated plastic holder to prevent scratches. soon to be on all NGC holders!

Dave Goldsmith

American Rare Coin Galleries