Edit: Gah, misspelled identifying

So, here's the deal.
I spent two weeks last summer in a town called Les Sabled D'Olonne in the Pays-de-la-Loire-region. After checking some maps, I found this spot on the map called "Blockhaus Epave Infernet" located on a large beach and I thought I'd check it out.

- A map showing Pays-de-la-Loire and Les Sables-d'Olonne


Local map with the Blockhaus at the red ring.





At Plage de Sauveterre, there was a big underground bunker system and at the Blockhaus, it looked like this:


You could still see where all the trenches had been but the bunker was closed for good.



- Inside the bunker who had fallen down to the beach, you can see there has been some kind of gun there but they had blown it up in later years.
(Sorry for bad pics, both or cameras were broken so I had to use a disposable.)

One day I found a relic and it looked like this:

As you can see, it is around 88mm across so my first thought was 'Hey, it's from an 88!', but I'm not sure. It has probably lied in the water for some time because there's small rocks attached to it and it's almost falling apart.




- The backside. I've seen pictures from some kind of ammo-container and I think it's from one of those.
Me and my dad speculated that they might had units placed in the woods because they had a road-network behind the beach.
I have searched the internet for information but found none.

The questions:
- Does anybody know anything about german units on the west coast of France or in this area?
- Does anybody know anything about this bunker, and the soldiers using it?
- What kind of relic is this and where is it from (Who used it and so on..)'

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