Started with filing on the surface to get some of the pits out before I thought of taking a picture. Surface isn't even flat as you can see the low spots and the pits in the surface.
Started with 200 grit, then 400, then 600 grit block sanding. Decided this is good enough. We shall see. Reinstalled and after a 5 minute test, watching the edge of the filter, it's not leaking......
