I recently bought a 3rd gen G23. I notice there is nothing holding the front sight to the slide. No nut, no threaded post. There is a bathtub-shaped raised area surrounding the interior side of slide slot. Looking into the slot I can see a shallow untreaded hole in what is probably the bottom of the sight blade. I see no stake marks. It's like the sight (tritium night sight) has been glued in place. Appreciate any information. Thanks.