I asked a locale dealer, who suggested it could be metal deflection. I don’t know. The area is raised, flat, with well-defined edges. I did the toothpick check to make sure it’s not a bubble. I’ve found two similar 2005’s as well. Nether is the identical to the one in the pic.
It could possibly be a filled die, but looking at the lines in the close-up I'd guess it was the result of die-polishing. Just my guesses, will leave it to the experts Interesting find.
I just recently found one of these myself. I also have a Washington quarter with the same problem. Hmm.. worthless?
I’ll bring this post back to life.:goofer: I found this 1996 quarter yesterday. It’s pretty dinged up but the die abrasion is there. Maybe I’ll try to find a type set.