What is this?

[Dan00001]

This is up a local hill. I'm guessing it's for some sort of surveying equipment but it's not at the highest point of the hill.

 

[Billy-o]

It's the valve they use to pump up the planet. Leave it alone or we'll deflate.

 

[TLM]

Here that would be either a surveyors point or a corner in a lot.

 

[Pattree]

Is it old enough to be military?
It looks something like the mounting point for an old RAF direction Finder.

Edited to add:
Do those marks in the concrete point NESW? I have no idea how significant that might be.

 

[Dan00001]

I did notice the markings but didn't take a bearing. I will next time I am up there, though.

Doing a reverse image search, the only thing I could find that looks similar is this:

File:Borne Cadastrale Route Coudes - Saint-Cyr-sur-Menthon (FR01) - 2020-11-07 - 2.jpg - Wikimedia Commons

commons.wikimedia.org

With this description:
Borne cadastrale le long de la route des Coudes, Saint-Cyr-sur-Menthon.

Which translates to something along the lines of boundary marker.

I did message The Map Reading Company on Facebook but they've not replied to me yet.