just purchased a 89 XJ wagoneer limited

just above the rear view mirror, on the headliner is what appears to be a black button, or some sort of cover for an interior light. it is black plastic.

i am unsure what this is. my guess is a map light? or something that comes on when the 4x4 is engaged?

it is located where a sunglass holder would be in most new vehicles.

I will add pictures tonight, but if someone knows off hand that would be awesome!

Thanks!