I would say your right. Most likely a die gouge, couldn't see it being a die clash cause there is no straight lines like that on the obverse. And I haven't found anything on the Iowa doubled die reverse. But wait till the more knowledgeable users reply
I would say DDR. It's centrally located and in the same location on the die as the other 2 Wexler has listed. It's just the roof, not the window. Nice. By the way, I am pretty sure I have found a couple DDRs on the Fort Moultre quarters. The underside of the coat on the soldier. Be on the lookout. I'll get around to taking images sooner or later.
If he's still around ( I know he's pretty busy ) check with @Heater to see if he's found anything similar. Looks like it (could) be doubling. If it's not listed with Wexler, it does not mean it might not be a new unreported doubled Die.
Still around, busy and it is Hot out there. Felt like a stroke out there yesterday. Boss told me to quit early today cause of the heat and he was buying the IPA's. Quarters are not in my scope of minor doubled dies that no one cares about. I do care if the OP does though. Looks doubled to me. Surprisingly, no one has asked for a pic of the obverse yet. Don't worry, some stick in the mud certainly will. and don't forget that it is not worth anything. Who would want such a minor error.
OP, ignore my sarcastic reply. It was not directed at you but the my sheet don't stink peoples. Your find will most likely be put down at some point. Minor, no value, who cares, etc....Ignore them and nice find.