Great job! I was going to suggest snap-ring pliers, or two small drill bits clamped in vise-grips, in the vent holes. But those two little spot-faced areas came in handy. I've worked a lot in manufacturing, and am wondering why they are there. I figure they have something to do with fixturing for the slotting process on the face of the cap.
That's a good point about how the camera being stored upright avoided extensive damage.