The die crack usually isn't a factor unless there is a field break and/or surface displacement. The 1921-D is an exception as these dies were overused to a point they literally disintegrated. A notable non-21 die crack is the 88-O scarface.
In order to assist with this 84-O we will need to see pics of the entire obv/rev.
Ok, these should be a lot better. High resolution photos taken with a 100mm Macro lens. I don't have a good enough eye yet to attribute the mint mark. The best I can do is say that it is a far date (I think).