Mine has no screws at all, and a close look at your picture shows it's exactly the same as the one I have in front of me on my desk. The two notches are for the aperture pin and the square tab.
I agree that it it was probably glued from the manufacturer, but what sort of glue ? I don't know, and I'm disinclined to pull the shroud off mine to try and find out.
Personally, I would look carefully and see if any remaining residue from the original glue is in place, then I would also try and carefully remove the old glue.
I would use a soft glue, a contact glue, that could be prized apart if the need arises. It's not structural, all it has to do is keep the shroud in place.