David Aber finds lots of mailboxes in parts of town that I don't reach on my bicycle. Here's one he calls “The Little Engine That Could.” He wrote that it's “made of steel … The homeowner is a retired metalworker from TEP. Obviously skilled.”
He emailed the photo on October 6th.
Update (November 23, 2020): There's another locomotive mailbox at 7046 Flamenco Place.