Could be a port permit, but someone from NJ can probably verify it... I think it possibly could be the registration sticker (tax) for New Jersey ( similar the one you put in the middle on the rear on the license plate in Sweden),its usually stuck on left side of windshield ( here in Texas,bottom center in Virginia, could be right side in NJ???looks like its right side in pic..), it would have an expiration date , for one year at a time...so , its very likely the windshield the car had in the US.
