How to tell for sure that it is a Grease Filled Die issue? Note the devices on this obverse on United? Note how they look wider than normal? That is because the were almost totally filled on the die, thus why they look wider, because the tapered area was full, preventing the strike on those devices.
Thus if you see the devices wider than normal at the base, it was a Grease Fill issue.
CoopHome: How can your tell if a Grease Fill on a die is present on a coin? wider devices at the base