As mentioned; hard to tell from just the one photo. Please post Full Image (click on Full Image after the photo has uploaded) pictures of the entire coin, obverse and reverse, for better opinions. Most likely debris on the die as the rim isn't flattened, as it would likely be if it was just damage.
It really is helpful with full photos. A weak strike does not occur on only one side of the coin. Sometimes a tilted die can cause a weak strike on just part of a coin.
I would say design weakness due excessive die wear. Could be a bit of grease in there, but ether way there is no value added because of it, and has very little numismatic value except as a study piece on die wear. JMO.
I think it's DD. worn die. Grease strike affects the majority of the devices as does weak strike. It's a pretty common coin either way. I've learned that if an error is not completely obvious, or some part of a series of errors leading up to something obvious, to not to get my hopes up. But I still always check in with the vets here.