[vectorit]

The outer pair of holes are for the sun visor clips.
The center larger hole is for a large round head phillips screw.
The inner pair of holes, look to me like someone drilled them for something. Perhaps a bracket for a CB, or a stetson hat holder bracket, or?

The older burbs (as in my 1968) had the rear view mirror screwed on there in the center, but those holes are to far apart for the early style rear view mirror bracket.