So as all others mentioned ,hope there is no cement or glue involved and the Tube can be reinstalled. Maybe there is a chance to fill the countersunk with some type of liquid metall exposy. I have done it in the past by the same problem on a watch. After this is done some drilling and retapping an I think when the Tube is installed again you can't see it.
Maybe this is no necessary hard to say from the Pics.
So Bert if u need my help let me know.