Trying to remove this mail box from the post.
There are five of these fasteners which I believe are holding the mailbox the mounting plate.
Appreciate your suggestions and feedback.
Those are pop rivets. They are not for removing.
The product would have been sold with those permanent fasteners already installed. The mailbox was installed on the post after those were attached, therefore they cannot be important to removing the mailbox from the post.
You can remove them if you really want to by drilling them out, however this will prove to be a waste of time.
Have you looked inside the mailbox proper? Sometimes screws hide there.