No apologies needed! The only reason I knew it was called "screw cover" was some kind person on this forum told me. I was googling "window trim" and couldn't find anything until I posted a pic here. Hehr was the brand of windows that were put in these campers. I don't believe the screw cover seals anything, I see many campers with them missing, it's just to cover up the screw heads. I believe your unit is early 90's, and the screw cover is different that our 85. Ours is a rigid piece, like Janalee says, that we cut and snap in. I think yours is more bendy. Our windows do not have curves at the corners. Perhaps someone with that model year can answer better than I can.
Jenny & Andy Turner
Bowley's Quarters, MD