On May 20th, I just happened to be riding far enough on Fontana Avenue that I spotted two similar mailboxes eight blocks away from each other. You saw the first box, at 2520 N. Fontana, yesterday. (If you didn't, you can click there.)
Here's the second box, the one farther north. It's black, with the house number and a saguaro between the posts.
(I normally don't show saguaros, but this coincidence made the boxes worth showing.)