Realcent.org

I saw this auction for a 1870 penny real nice coin, but it said PCGS genuine not gradeable. I had never seen that before, what does that mean?
http://cgi.ebay.com/1870-INDIAN-CENT-/2 ... 3366498f24

this particular coin was thought to be cleaned

scroll down to the section on problem coins in the following link

http://www.pcgs.com/grades.chtml

the two numbers after the period are the code -- in this case 92 -- cleaned