Looks like a rusted crown wheel there. i have had some luck in the past with Simichrome polish and a little elbow grease. If you can't find any way to take it off let me know. I have a non-operative gen 6497 crown wheel you can have.
Maybe some 200 grit wet sandpaper would work too..Just a thought.
You can remove the screw and take the crown wheel off, just beware of the click and the little click spring that sits underneath the crown wheel. Might be easiest to remove the click and spring too,but watch that the spring
does not fly away on you.