Those are really neat-looking! It was the old DDO-001 but at some point Dr. Wiles changed his mind and de-listed it from the CONECA files. Wexler has left it up, and no one really seems to know for sure if it is a DDO or just some odd die gouge.
Looks like the mint tried to polish it off the die. You might want to send this image of the polishing to attributers to show them what you discovered on your example. They might like to see those images?