Phil,
You are definitely missing a screw and it would be installed from the outside, not the inside although I know that was the case on some forends and then the tip of the screw was engraved.
I don’t have a close up picture of a Knick forend handy but I will post a picture of a few Ithaca Single Barrel Traps that I quick took before the owners chased me away at Rock Mtn a few weeks back
You may have to zoom in to see the screw that is missing on your Knick