Anybody ever seen this error before. I've searched lots of websites and can't find a thing about it. One of a kind maybe?
Debris Inpacted Die , usualy refered to as Grease Filled Die. I have seen people post these coins with a missing "H" also. I don't believe it would be "One of a kind" as the Inpacted Die will run until the inpactment falls out or the press is stopped to clean the dies. It is hard to say how many Errors like this there are made, as with most Errors. I hope other will comment also.
It's very very common - this exact filled die on the Bicent. Half. Other letters are known missing too. I have one right now in my pocket change that I will spend in the next few days. I have one with the last "E" missing. There is no premium on it because it is so common, and fairly easily found in any group of Bicentennial Half dollars. You might want to keep it as an interesting conversation piece.