I have specialized in rare coins and die varieties for 30 years. I'm a buyer at shows and auctions and pass savings on.
What many coin buyers do not realize is that the vast majority of 19th century coinage has been doctored. Wire brushing, polishing, artificial toning are all tricks that have been played on coin buyers. This is the reason that third-party grading came about in the first place. Generally, (not always) buyers are safe from these abuses with PCGS, NGC, and ANACS coins. The strength of Prestige sets, proof sets and uncirculated sets is that these coins are sealed by the US mint. However, they must be properly stored to prevent PVC damage. This also pertains to certified coins which will degrade in hot environments. Buyer Beware and purchase wisely.
I don't buy abused coins unless the coin is so rare that the coin is still desirable in the market. If I offer a coin with problems it will be described as such and discounted. Accurate grading and integrity are my hallmarks.
Steve Koteles