The Mint factory has its share of dirt, grease and other lubricants, and metal filings. The recessed areas of the dies sometimes fill up with a combination of this foreign material, preventing the metal of the coins from flowing into the incused areas. This results in weak designs or missing design details. The filled-die coin is one of the two most common types of errors.
how to determine value? Not to sell as it took me quite a while to locate coins from looking at enough to make my eyes cross.
Do i put it in a safe or is the value more like a box on the dresser...?
There's really not much value for this kind of error unless the grease takes out alot of detail i would say yours is a nice one because it took out some letters even through there's not much value for them .
Well if you decide to sell it you may get 5 bucks on ebay depending who wants it.
I would say it's a keeper for your collection. I also think it's a good example for a novice to have a learning coin.