The window frame is off a vehicle which originally had a canvas roof/rear cover. It would have originally have a curved metal top rail with hooks on it , pop riveted onto the frame through those holes . An original hard top/ truck cab/ station wagon window does not have them. Item 13 in the picture
This shows the part better, it shows the holes, and also the external sun visor .
.The top rail also is bolted on the inside in the same place as your roof panel.
Good information. Now I need to source one of those visors from somewhere.
The Exterior sun visor complete Kit part number was 503979 then 608551 then - 90608551 and finally GLR330 . Rovers North list it ,see https://www.roversnorth.com/search.a...&submit=Search.
If you are tall it can inhibit the forward upward view.