I grant you that there is a risk in sending off a coin for preservation but that is why that PCGS, NGC and other Third Party Grading Services that have divisions that offer coin preservation/conservation, insure the customer's coin for it's value. If they damage the coin during conservation, certification, grading and slabbing, they will purchase the coin from the customer at it's true value. I buy, sell and trade coins as part of my' small business selling collectibles and I have seen nightmare scenarios of cleaned coins by conservations services but have seen many more, cleaned by private individuals that thought they knew what they were doing when they cleaned a coin. In fact, I have seen rare coins that were valued in the tens of thousands of dollars, reduced in value to mere hundreds of dollars because the owner thought that he/she had to clean the coin before offering it for sale. One of those was an 1895 Proof Morgan Silver Dollar, the rarest and most valuable Silver Dollar in the Series. While soap and water can and will do wonders for some coins, it does not conserve the coins and protect them from further deterioration which conservation services do! Also, you never clean a coin with a brush as it will leave fine brush lines on the surfaces of the coin. If you are going to clean coins such as large Coppers, then after a light bath in soap and water, rinsing and patting dry with a soft towel, you should soak it in mineral oil for up to 3 weeks, rotating the coin every 3rd or 4th day to insure good saturation of the mineral oil into the dirt, grime and some of the corrosion to loosen it. After having soaked for the 3 weeks, remove the coin and remove the dirt, grime and any loose corrosion with a green Rose Thorn (*), rinse with water and pat dry with a soft towel. If the coin still has unwanted dirt and grime, then place it back into the mineral oil for a week or two and repeat the above. Once finished with the cleaning, pat the coin totally dry with a soft towel and place it in a protective holder. (*)As footnote: A green Rose Thorn will not scratch or damage the surface of a Copper coin. If you see such on a Copper coin, then it is scratches through dirt and grime that still remains on the surface of the coin.
Frank
Most people that send a coin in for grading, are VERY disappointed in the outcome, and in the grade they get back. Actually reducing the value of what they thought they had. I had an 1859 seated quarter that I thought for sure would make AU-50 or 55. Instead....with no explanation mind you..., it graded VF-45. Knocking the price of the very next grade down by 1/2. By the way.....don't think for a second these coin, (and sports card), grading companies look at population reports, to manipulate prices of certain coins and sports cards. Would it have made any difference in my coin? NO! But then again, on rarer varieties,...Absolutely! At the time my graded VF-45 would have sold on EBAY for about $40-45. (I know this because it didn't reach my reserve of $55) So I cracked open the holder, took out the coin, and someone bought it for $70, ON EBAY. Quite a difference from some, so called experts opinion. And by the way....the $70 price was, at the time, still under the $100 value of VF-45. (I think it's higher now as I only have the 2010 RedBook. This brings up another thing.....These coin price books ARE A GUIDE ONLY!!! Most coins sell for quite a bit less than the guide prices them at. AND.....most people grade coins much....MUCH higher themselves than they actually have. Most in THIS forum don't want to hear the truth about his or her find. I'd soak that coin in warm distilled water for a few days to break up the dirt. Then warm some peroxide and use a Q-Tip to remove the dirt till I was satisfied. THEN....I would seal it with olive oil or vaseline. As IP said.....I would have already done it....and the coin would already be listed in "My signature" as SOLD! 
