Realcent.org

Tell me what you think. Weak mint mark, general wear? It is hard to see in the picture but looking at the coin directly you can make out what appears to be a faint D. The rest of the coin doesn't seem to have much wear on it. All Nickles of course have mint marks so regardless of of whether it is a D or P something happened to it

probably just a grease filled die

yes, mostly likely filled die.

But it is a 2009. That is somewhat rare.