[Bill Rose]

After looking at all the pictures of original caps with black paint, they all have paint only left in the center/top of the caps. It seems like the caps were plated like the radiator caps, with nickel plating? Then the paint came off very easily, where your hand/fingers touched the cap to remove it.
Seems like the painting was an after thought. Maybe just a way to paint the pump, without getting paint inside the pump. I guess if you want the paint to stick for any period of time, it should be blasted first.