I was finally able to see the pics from the post over at cj-8.com. The photos weren't designed specifically to show off the center caps, but they do give us an OK picture of what they should look like. The pics were fairly high resolution so these are crops showing just the center caps.
We can see that the black background should be continuous, as has been stated. There is some variation in the darkness, probably because these have not been repainted.
"I give you a republic, if you can keep it." - Benjamin Franklin