Frank, coins struck by grease-filled dies are very common. All of the machinery used at the Mint require lubricants to keep them functioning properly. Planchets can come into contact with these lubricants and when they are struck, a small amount of lubricant is transferred to the dies. Dust particles in the air will adhere to these lubricants and can build up in the recessed letters of the die. Continual striking compacts this grease and debris until it finally fills the recess and it looks as if there is no letter at all. You can find examples of coins struck by grease-filled dies in almost any denomination, year or mintmark. Chris
The state quarters were really known for these grease fills and each one seemed to have it's own favorite spot for the fill to occur. On DE it was the last E in State, on CT it was the middle letters of Charter Oak, on NH it was the mintmark on the obv. they are all common and are not worth a premium. (The no E in State DE was hyped a lot back in 1999 and did bring a nice premium for a short time THEN.)
