Maybe. But it looks like it was struck normally. Are you sure it is not some black gunk stuck to the coin?
"lighter part (TH II) is actually lower than the rest of the coin" that would generally indicate it is but the pictures don't show this. can you take a picture at an angle with a macro setting?
It looks like a de-lamination of the planchet, This link has some clues on how de-lamination occurs. http://www.australian-threepence.com/blog/2008/11/peel-or-lamination-flaw-coin-error.html