Here's another mango tree with its fruit up for ID. I'm pretty sure I know what this but want to ask everyone without giving my opinion so no one's answer is influenced by what I say!
This is another of those that it is much easier to say what it is not, than to says what it is for sure. A cut open fruit would be helpful. In the running would be Carrie, Alphonso, or, possibly, but not as likely, Fairchild or perhaps even some others.
Harry