I know that has been around a long time and maybe a member of your family put them in.
Not to say anything bad about them but on a light hearted side if they are anything like the people on my street they are in maybe 6 inches.
I have never in my life seen so many leaning flopping mail boxes.
It takes a lot of work to put a 2 foot hole in the ground here.
You need a big heavy rock chipping bar and post hole diggers.
Worth