Yep, our neighbor down the road back in Michigan had one similar to
that, but of his own design. His swung on the horizontal and reset bu
way of an angled cut and its own weight. He went one step further and
"armor-plated" it - The entire area around the mailbox itself was
enclosed in those plates that go between the rail and the tie on
railroad tracks welded up to form a seriously impressive bit of
armoring.

Guy near us has his on a swivelling beam. At the other end is a
counterweight. A screendoor spring holds it in the Box Out position
against a stop pin.
When smashed, the assembly swivels. The iron counterweight usually
get the rear quarter of the car.
We have been having Coyote Vs. Roadrunner wars with the vandals for
decades here.
My passive approach has been the simplest and most effective. Bought a
regular aluminum mailbox, unfolded it for a pattern. Cut a steel
tube (1/4 wall) longitudinal to get the top radius. Flame cut the
door and rear plate, and side rectangles from 1/4" 18 Nickel maraging
steel, and welded it up. We change the paint color every few years.
So, we recover broken aluminum baseball bats (I never knew they were
filled with urethane before), and even an abandoned crowbar. We heard
the screaming and the *GONG* sound when they hit the box with it.
Must have stung. The box is welded to a piece of concrete filled
Lally column.
The mailman loves it, as it looks exactly like a regulation rural
box...Stealth, you might say. It sounds like a vault when slammed
closed. The local hardware store wnted to retail them if I decided to
make them. Nope, don't need the liability, but a fun project.